Future Perfect

Higher-Kinded Types for normal humans

Fri, 06 May 2016 11:18:17 -0400

If you’ve heard some of those people talk a bunch about how language X is better than language Y because X has “higher-kinded types”, and wondered what that even is and why it’s such a big deal, you might have found yourself in the same situation as me: googling for answers, finding a bunch of whitepapers and overly-convoluted answers about “Functors”, “Monads”, “Typeclasses”, and other things that sound like they belong in a college math class somewhere.

Thankfully for me, I managed to track down a guy who explained what they are and why they matter to me in a way that made sense and didn’t need theorems or proofs (“rightfold”, if you’re reading this somehow, thanks!).

So let’s dive in.

I’m gonna talk in terms of Java, because it’s pretty familiar to me, and it’s pretty familiar to most coders out there. It’s also pretty good at illustrating the point.

See, recently, Java gained a support for lambdas, and a couple of other useful concepts: Streams (for efficiently saying “I have a bunch of values that I can send through a pipeline”) and Optionals (for safely saying “this value may or may not exist”, without NullPointerException headaches).

Now that Java has lambdas, we can write functions that take other functions in as parameters. So now not only can I take in an Integer, I can also take a function that turns a String into an Integer – in Java 8’s terms, this is a Function<string integer>. If you’ve heard of the Strategy Pattern in Object-Oriented design, this is probably really exciting to you, because you no longer need a bunch of anonymous classes and other boilerplate.

So now I can write this function:

Before we go further, I’m gonna change up the way we talk about function signatures a little bit, for the sake of cutting “right to the meat” of the function. When I say public X foo(Y y), I’m talking about a function that takes in a Y as a parameter, and returns an X. From here on out, I’m going to describe functions like that as Y -> X, or “a function that turns a Y into an X”

And when I talk about a function that takes a Y and a Z and hands me back an X, I’ll call that Y -> Z -> X, to say that it takes a Y, then a Z, and then gives me back an X.

If I haven’t lost you yet, great. With this “cleaner syntax” in hand, let’s talk about our parseNumbers function.

With our new syntax, a function that takes a Y and gives me an X is Y -> X. So then our Function<string integer> can be written as String -> Integer (see? much easier to see what’s happening).

So what about parseNumbers? It takes a Function<string integer> (that is, a String -> Integer) and a List<string>, and it hands us back a List<integer>. If we just write it as String -> Integer -> List<string> -> List<integer>, we’d be talking about a function that takes a string, then an integer, then a List<string>, then a List<integer>… you get the idea. Since our parseNumbers is a function that takes another function, we have to describe it as (String -> Integer) -> List<string> -> List<integer>. We throw parameters around String -> Integer to make it clear that it’s really just one argument that happens to be a function itself.

Functions like this that take other functions in are called “Higher-Order Functions”, because the people who think about these abstract concepts like to use abstract terms to avoid getting caught up in the details of any one language.

You can think of the whole “higher-order” thing like this:

A “normal” function that takes plain old values is first-order accepts parameters, and gives you a value. Done. We call those “first-order” functions.
A function that takes first-order functions is one that takes parameters that take parameters. So you can think of it as “second-order”. “Second” is higher than “first”, so it’s “higher-order” than just a normal “first-order” function.

Really, that’s all there is to the whole “Higher-Order” jargon

Now, if you’ve written much code in Java 8, this is probably not new to you. In fact, you’ve probably made good use of one function that takes other functions: Stream’s .map(Function<a> f) function. You use it like this:

Stream’s .map function takes another function that turns something from type A into something from type B. In other words, it takes an A -> B. It uses that function on every element in the Stream<a> to give us back a Stream.

So then, .map looks kinda like Stream<a> -> (A -> B) -> Stream. It’s really useful for dealing with lists, especially when you have a bunch of those A -> B functions in a row, turning A -> B then B -> C then C -> D…you get the idea.

There’s another one of these you’ve probably used in Java 8, and it’s also called .map, but it belongs to Optional<t>. Optional<t> is a useful class that wraps around another class to handle whether a variable is null or not, but, thanks to .map, it’s a lot nicer than just doing null checks the “normal way”:

As demonstrated here, .map on an Optional<a> takes in an A -> B function, uses it on the A that is “inside” it, and gives you an Optional. Much easier to read than a big “pyramid” of cascading null checks.

So .map here looks like Optional<a> -> (A -> B) -> Optional.

But wait, if you swap Optional for Stream, you’ve got the same as Stream’s .map function. In fact, you could swap in List or Set or Collection or some kind of ErrorOrSuccess or any other “thing that holds other things” class.

The concept behind all of these are the same: they’re classes that wrap around another class, and let you “transform” that inner class by handing map a function.

It’d be nice if we could write functions that can deal with any of those “map-able wrappers” and use their “map” functions.

So let’s start with an interface.

Except wait, if we write functions that take a Mappable</a><a>, any time we use that function, we’ll have to do a bunch of annoying casting.

And there’s another problem: we can’t go back and retroactively add this interface to existing classes (like Stream or Optional). We’d have to define a class that extends our Mappable interface for every single existing class out there that ever had a .map function.

Obviously that’s a lot of bloat and pain.

If only we could just tell the Java compiler that our code accepts anything that’s a “wrapper” for another, inside value.

This is where Higher-Kinded types come in.

Remember how we said that a function that takes something of type A and returns something of type B is A -> B?

What if we could do the same thing with our types themselves instead of just values? After all, generics like Optional<t> are really just a way of feeding in some other type parameter – like String – and giving us back a type that talks about Optional of String specifically so that the compiler can tell the difference between an Optional of a String and an Optional of an Integer.

So really, generics are kinda like functions for types: you give them a parameter, and they return you something back. Only instead of taking a value as a parameter and giving you a value back, they take a type as a parameter and give you a type back.

We specify the “shape” of our functions by talking about what types they accept.

We can specify the “shape” of our generics by talking about what “kinds” they accept. “Kinds” are a way of talking about “types of types”.

For simplicity’s sake (and because I don’t know a lot about what kinds there are myself), we’ll just stick to the simplest “kind”: * – that is, “any kind of type”.

So just like before, when we had our A-to-B function as A -> B, we can write *-to-* type-functions as * -> *

Which means that just like before, when we could write functions that take functions as (A -> B) -> List<a> -> List, we can now write our type-functions-that-take-type-functions as (* -> *) -> *.

Put in more familiar terms, this lets us talk about the type of any class that itself is generic. (* -> *) -> * means “any generic type that takes one other type as a parameter.” And we can go even further: (* -> * -> *) -> * means “any generic type that takes two other types as parameters”

Higher-Kinded Types let us build a generic type over the concept of generic types. They let us write code that knows that the types it’s working on are generic, and can define functions or behavior based on that knowledge.

Like Higher-Order Functions, they let us reduce the amount of duplicate code we have to write by allowing us to abstract over another degree of similarity.

So what? Who actually uses this stuff?

If you’ve ever seen code that looks like this:

You’ve probable noticed how painful it is that Java doesn’t seem to realize how similar .flatMap and .orElse is across various generic types. Wouldn’t it be nice to be able to write code that knows we’re dealing with containers, and knows generically how to flatten them? We could even define a higher-kinded interface with a flatten function.

There are languages that have Higher-Kinded Types: Haskell and Scala are the only two fairly-mainstream ones I’m aware of. They come with other fancy type system tools (like implicits and typeclasses) that supercharge Higher-Kinded Types even further, but those are another topic for another time.

Notes on evangelistic hesitance

Sun, 01 May 2016 20:25:44 -0400

Why do I hesitate in evangelism? What holds me back from being as obedient as I ought?

Fear of my inability
- But of course I’m unable. Is it not Christ and the Gospel that saves, or is it my own power? Can I by persuasiveness alone make those spiritually dead to be alive again? Or does the power belong to Christ Jesus? We have this treasure – the Gospel – in earthen vessels – the most meager of containers – to show that the surpassing power belongs to God and not to us (2 Corinthians 4:7). If fear of my own inadequacy is preventing me from preaching the gospel, then I am assuming that obedience lies only in actually saving souls – something I cannot do – rather than in doing simply what Christ commands: proclaiming the Gospel.
Fear of my own sin’s effect in damaging my witness
- But if I must be a perfect person before I am a worthy example of the Gospel, then I am never able to speak its truth. If I am required to be perfect before I do as Christ requires by proclaiming His work, then His requirement laid upon all Christians impossible. And yet we know that unlike the full weight of perfect adherence to the law, “[his] yoke is easy, and [his] burden is light” (Matthew 11:25-30)
Fear of rejection by men, of “rocking the boat”
- This is nothing less than idolatry either of human approval or of current circumstance. To prioritize a genial relationship or a “calm sea” over obedience to my Maker and Savior reveals that which I really worship, in opposition to what I claim to worship.

Now the tax collectors and sinners were all drawing near to hear him. And the Pharisees and the...

Mon, 18 Apr 2016 18:25:54 -0400

Now the tax collectors and sinners were all drawing near to hear him. And the Pharisees and the scribes grumbled, saying, “This man receives sinners and eats with them.”

So he told them this parable: “What man of you, having a hundred sheep, if he has lost one of them, does not leave the ninety-nine in the open country, and go after the one that is lost, until he finds it? And when he has found it, he lays it on his shoulders, rejoicing. And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep that was lost.’ Just so, I tell you, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance.

“Or what woman, having ten silver coins, if she loses one coin, does not light a lamp and sweep the house and seek diligently until she finds it? And when she has found it, she calls together her friends and neighbors, saying, ‘Rejoice with me, for I have found the coin that I had lost.’ Just so, I tell you, there is joy before the angels of God over one sinner who repents.”

(Luke 15:1-10 ESV)

This love that God has for His elect would, in a human, be rightly considered reckless. It is a love that is willing to expend far more time and effort in seeking out a single lost sinner than that sinner merits.

And we must be clear in our understanding that this is indeed a unconditioned love; the analogy of a single sheep or a single coin is an unsurprisingly good fit (after all, the Creator of speech and of all things does not fail to find a suitable allegory). What merit is there in a single sheep that is not easily replaced by any of the other 99? What worth is there in a single silver coin – less than a day’s wages – that warrants spending an entire day’s work in finding it?

It’s not the intrinsic merit of the coin or the sheep or the sinner that drives this search, but the extrinsic valuation placed on them by the One who pours their much-more-valuable power into recovering them.

Such love and such unmerited care demand the fullest reciprocation possible, of the sort Jesus spoke about just before giving these analogies:

Now great crowds accompanied him, and he turned and said to them, “If anyone comes to me and does not hate his own father and mother and wife and children and brothers and sisters, yes, and even his own life, he cannot be my disciple. Whoever does not bear his own cross and come after me cannot be my disciple. For which of you, desiring to build a tower, does not first sit down and count the cost, whether he has enough to complete it? Otherwise, when he has laid a foundation and is not able to finish, all who see it begin to mock him, saying, ‘This man began to build and was not able to finish.’ Or what king, going out to encounter another king in war, will not sit down first and deliberate whether he is able with ten thousand to meet him who comes against him with twenty thousand? And if not, while the other is yet a great way off, he sends a delegation and asks for terms of peace. So therefore, any one of you who does not renounce all that he has cannot be my disciple.

(Luke 14:25-33 ESV)

This too sounds reckless, by human means; so deep a love that it makes all other bonds seem like hatred by comparison, and makes even death seem desirable if it means unity with the object of its affection. But this love is required of us as a dim mirror of the love that has been given to us.

To give anything less than this totality of love is hatred by comparison, and shows one unfitting of the sacrifical love that God bears for and to His own.

To hold any love higher than this one – for this One – saps it of its necessary vigor.

"And while he was at Bethany in the house of Simon the leper, as he was reclining at the table, a..."

Mon, 14 Mar 2016 08:15:53 -0400

“And while he was at Bethany in the house of Simon the leper, as he was reclining at the table, a woman came with an alabaster flask of ointment of pure nard, very costly, and she broke the flask and poured it over his head. There were some who said to themselves indignantly, “Why was the ointment wasted like that? For this ointment could have been sold for more than three hundred denarii and given to the poor.” And they scolded her. But Jesus said, “Leave her alone. Why do you trouble her? She has done a beautiful thing to me. For you always have the poor with you, and whenever you want, you can do good for them. But you will not always have me. She has done what she could; she has anointed my body beforehand for burial.”

- Mark 14:3-8

It is easy to confuse humanitarianism with Christianity. After all, James 1 says that “religion that is pure and undefiled before God, the Father, is this: to visit orphans and widows in their affliction, and to keep oneself unstained by the world.” (James 1:27).

But while Christianity does motivate provision for the poor, the two are not the same, as Christ here points out. Had the woman taken the flask of perfume and done as her critics in this passage suggested by selling it for almost a year’s wages and giving that to the poor, she would have been doing perhaps a good thing, but a worse thing than pouring it over the head of Jesus.

Likewise, in our pursuit of extending the love of Christ to a needy world, we must never fail to pursue a love for Christ. We must not ever see any good thing as greater than worship of Him, lest that good thing become a rite to the false god of the appearance of piety.

And there is perhaps another element to the criticism that Jesus refutes here: notice that he says “you always have the poor with you, and whenever you want, you can do good for them” (emphasis added). These critics perhaps shared a pitfall still common to believers – to me – today: a failure to seek out means of obedience and service to Christ, and a jealous guilt in the presence of someone who is walking in such obedience. It’s possible that these men would not, having the bottle of perfume themselves, have thought to sell it and give it to the poor. But seeing this visible act of reverence for Christ Jesus may have stirred in them a guilt over their own complacency, kindling a jealousy and a desire to “equalize” themselves so that their own consciences might be quieted by their self-justification. They may have stared in the face of active obedience and felt their image of being “good people” come under scrutiny by comparison.

Or perhaps not. Perhaps I am reading in this passage a sin of my own that was not, indeed, present in those people present that day.

But I know that Christ’s words and actions here teach three things to my sin-marred mind:

Worship of Christ Jesus is the foremost priority of Christ’s own.

We are not, by our outward appearance of piety, excused from the eager pursuit of our Lord that a right love for him must necessarily inspire.

We are surrounded by opportunities to show our love for Christ by obedience to him towards others, so long as it is indeed a love for Him that drives us, and not a love for our “position” as “good people.”

We see in Genesis 3-7 the beginning of a cycle of sin and punishment: Adam, Eve, and the Serpent in...

Sat, 02 Jan 2016 12:53:34 -0500

We see in Genesis 3-7 the beginning of a cycle of sin and punishment: Adam, Eve, and the Serpent in the garden of Eden eating from the tree of the knowledge of good and evil, and consequently receiving the Curse; Cain murdering Abel, and being banished to be a fruitless wanderer on the earth; the generations of wicked men, whose every intention “was only evil continually, destroyed in the flood.

Yet we also see God providing mercy in each punishment: even as He pronounces the Curse to Adam, Eve, and the Serpent, He foretells Christ’s coming (Gen. 3:15); even as He declares Cain a wanderer and a fugitive on the whole earth, He marks Cain as one not to be killed and extends his vindication to anyone who kills Cain; and even as He destroys the generations of evil humanity, He spares Noah – and through Noah spares His created race.

This is telling of God’s character: He is just and loving. He is willing and able to punish, and He is also able to grow and refine His people through that punishment. His justice is devastating, but not hopelessly destructive. He is merciful, and He is kind.

To be like our Father, then, requires that we as Christians not only respect God’s justice and be willing to punish when necessary, but also that we seek to mirror His mercy; using punishment not simply to inflict dissuading pain, but also to encourage growth towards right obedience to our Father, just as He does for us.

There were some present at that very time who told him about the Galileans whose blood Pilate had...

Sat, 26 Dec 2015 11:57:24 -0500

There were some present at that very time who told him about the Galileans whose blood Pilate had mingled with their sacrifices. And he answered them, “Do you think that these Galileans were worse sinners than all the other Galileans, because they suffered in this way? No, I tell you; but unless you repent, you will all likewise perish. Or those eighteen on whom the tower in Siloam fell and killed them: do you think that they were worse offenders than all the others who lived in Jerusalem? No, I tell you; but unless you repent, you will all likewise perish.”

And he told this parable: “A man had a fig tree planted in his vineyard, and he came seeking fruit on it and found none. And he said to the vinedresser, ‘Look, for three years now I have come seeking fruit on this fig tree, and I find none. Cut it down. Why should it use up the ground?’ And he answered him, ‘Sir, let it alone this year also, until I dig around it and put on manure. Then if it should bear fruit next year, well and good; but if not, you can cut it down.’”

(Luke 13:1-9 ESV)

God’s timing in dealing his justice is his alone. We, his creations, ought to be wary of proclaiming it God’s justice when we see trouble befall someone, and to likewise be wary of declaring God slow to act – or trying to “invoke” his justice – when we see unrepentant sin unpunished.

After Jesus tells the Parable of the Sower, we see this exchange between Jesus and the 12...

Tue, 22 Dec 2015 12:45:21 -0500

After Jesus tells the Parable of the Sower, we see this exchange between Jesus and the 12 disciples:

And when his disciples asked him what this parable meant, he said, “To you it has been given to know the secrets of the kingdom of God, but for others they are in parables, so that ‘seeing they may not see, and hearing they may not understand.’

(Luke 8:9-10 ESV)

Jesus explains two key aspects of God’s revelation here:

God gives it to some “to know the secrets of the kingdom of God”
Jesus used parables so that those who are not thus given knowledge from God will “not see” and “not understand”.

From the first aspect, we understand that understanding of divine truth is given by God. This then implies that such understanding is not and cannot be obtained by human effort alone, especially seeing how Jesus refers to such things as “secrets of the kingdom of God.” Those things which God has chosen to keep secret cannot, by nature of His omnipotence, be disclosed unless He chooses to disclose them. So then, we cannot hope to understand them unless God gives us understanding.

This is consistent with 1 Corinthians 2’s description of “secret and hidden wisdom of God”, that God reveals to us through His Spirit, and which “the natural person” (the person without the Spirit of God) “is not able to understand…because [such things] are spiritually discerned.”

However, from both passages we see not only a proclamation of the futility of human wisdom, but a promise: God does give understanding to those to whom He gives His Spirit. We are not left blind, unable to discern truth or to know God’s character, but we are enabled by His mercy to understand His revelation.

The second aspect of God’s revelation that Jesus here addresses is, though less popular, equally in line with God’s character: that revelation of divine truth is given in such a way that some will not understand. Jesus says that he spoke in parables so that those without God’s elucidating work would not understand. There is no accident here, nor was it something merely unavoidable that Jesus otherwise would have prevented. God has, in His sovereignty, decided that some people must indeed pay the full penalty of their own actions. There are some whom He has not chosen to save, and these he allows to continue in their natural ignorance of spiritual matters. These are not given divine wisdom.

That there are some to whom God chooses not to give divine wisdom does follow logically from understanding both the omnipotence of God and the fact that, as discussed before, God gives understanding to some. This implies that not all are given understanding, and that while God is capable to give understanding to all, He elects not to do so out of divine prerogative.

This is a hard truth, but one confirmed elsewhere in Scripture; 2 Timothy 2 speaks of “vessels….some for honorable use, some for dishonorable”, and Romans 9 speaks in the same terms of a potter’s right to choose the purpose for each of his sculpted vessels.

As people not privy to the full designs of God, we may look at this and deem it unfair or even arbitrary. Why should some be instructed and saved, and others be left without understanding, and condemned?

We should note, of course, that there is a degree of revelation about God’s character which is available to everyone; Romans 1 tells us that “[God’s] invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world”, but that sinful man willfully ignores it, and they “by their unrighteousness suppress the truth.”

So those in ignorance are not in an innocent passive ignorance, but an obstinate active ignorance: they do not simply lack information, but choose to ignore the truth.

The picture of our real state now comes a bit more in focus: it is not those who are denied divine wisdom that are the recipients of unfair treatment, but those who are given it. No man deserves the saving wisdom from Christ, yet to some Christ has chosen to show mercy. All men deserve the active ignorance which they – we – choose in obstinance.

For God to choose to withhold the full truth from some who have refused the small portion they are given is then not unjust, but rather is perfectly just – He is allowing them the ignorance they deserve and have chosen.

And when the Gentiles heard this, they began rejoicing and glorifying the word of the Lord, and...

Tue, 15 Dec 2015 07:10:18 -0500

And when the Gentiles heard this, they began rejoicing and glorifying the word of the Lord, and as many as were appointed to eternal life believed. And the word of the Lord was spreading throughout the whole region. But the Jews incited the devout women of high standing and the leading men of the city, stirred up persecution against Paul and Barnabas, and drove them out of their district. But they shook off the dust from their feet against them and went to Iconium. And the disciples were filled with joy and with the Holy Spirit.

(Acts 13:48-52 ESV)

Paul’s preaching in Antioch elicited a tremendous response: not only were many saved, but “people begged that these things might be told them the next sabbath” (v42). The people were hungry for the message of salvation, and received it readily with rejoicing.

But there were also those who in obstinate opposition to God incited persecution. This too was an intense response: it was not enough for these to disbelieve or oppose Paul and Barnabas – they felt it necessary to create persecution against Paul and Barnabas through manipulation. They were not satisfied with being at odds with the truth themselves, but went further to create trouble and stir up violent opposition against God’s people.

But see the reaction of Paul and Barnabas, and of the disciples:

But they shook off the dust from their feet against them and went to Iconium. And the disciples were filled with joy and with the Holy Spirit.

For Paul and Barnabas, declaring the truth of the gospel was enough, and seeing its work in the lives of some was cause for joy. The disciples were able to “[shake] off the dust from their feet” and continue on in their ministry trusting in God’s inevitable victory over sin, and over the hatred of men towards God’s people.

There is no anger mentioned, nor bitterness; rather, simple trust in God’s timing. Indeed, it is through Paul that God would write in Romans 12:

Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, “Vengeance is mine, I will repay, says the Lord.” To the contrary, “if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by so doing you will heap burning coals on his head.” Do not be overcome by evil, but overcome evil with good.

(Romans 12:19-21 ESV)

This is a struggle I know too well. In the face of wickedness, hate, and manipulation, I so easily become angry. I so quickly long to be an instrument of condemnation on the obstinately guilty.

But that is not my role. Mine is to trust God, and to know that He works in His timing. He creates Saul of Benjamin and Saul of Tarsus, and only He knows his plans for each. He created Job, and he decreed Job’s trials – and he created the hate-filled false friends of Job – and though the moment of leprosy, loss, and accusation weighed heavy, it was God who spoke to condemn Job’s false friends, fully and rightly declaring their guilt in His own timing.

It remains true that only God can change the hearts of men, and only God has the authority to deliver final condemnation. We his children can only serve Him with patience and imitate the compassion He shows by waiting.

And looking intently at the council, Paul said, “Brothers, I have lived my life before God in all...

Mon, 07 Dec 2015 15:57:40 -0500

And looking intently at the council, Paul said, “Brothers, I have lived my life before God in all good conscience up to this day.” And the high priest Ananias commanded those who stood by him to strike him on the mouth. Then Paul said to him, “God is going to strike you, you whitewashed wall! Are you sitting to judge me according to the law, and yet contrary to the law you order me to be struck?” Those who stood by said, “Would you revile God’s high priest?” And Paul said, “I did not know, brothers, that he was the high priest, for it is written, ‘You shall not speak evil of a ruler of your people.’”

(Acts 23:1-5 ESV)

In this exchange, we see Paul under examination by the chief priests for simply declaring the gospel. Already he has been wrongly accused and unlawfully threatened by the crowd, and already he was nearly unlawfully flogged by the Romans. And now, the priests who are trying his case – judging him “according to the law”, as Paul points out – are themselves breaking the law just to antagonize him.

And Paul is unhappy with this, quite reasonably. He speaks up and points out the hypocrisy, but he does so in frustration towards the high priest, calling him a “ whitewashed wall” and angrily declaring God’s judgment on him.

The onlookers are astonished; Paul has just condemned the high priest, an office ordained by God. Though the man himself is corrupt, the office – and even the choice of corrupt man occupying it – are by God’s appointment.

There is then something to be learned from Paul’s response; though Ananias was clearly wrong, and though Paul was not wrong to be upset, Paul recognizes that his frustration has led him to break God’s word.

For many of us (myself included), it would be easy in this situation to remain angry, to insist on the other’s fault, and to (by proxy) insist on our own innocence. But Paul sees that there is a more pressing priority here: Paul cannot credibly declare the gospel of God (let alone “in all good conscience”) while also standing unrepentant in disobedience to it.

So Paul does what seems the simple thing on paper but is the difficult thing in practice: he repents. He confesses his own sin, sacrificing his own pride for the sake of the gospel.

Obedience, for a Christian, requires us to do likewise: we must regard our own glory as worthless and God’s glory as supreme.

In Acts 1, Peter cites Psalm 109 in suggesting that a replacement 12th apostle ought to be found in...

Sat, 21 Nov 2015 11:39:55 -0500

In Acts 1, Peter cites Psalm 109 in suggesting that a replacement 12th apostle ought to be found in place of the now-dead Judas. Psalm 109 reads (up to the passage Peter cites):

Be not silent, O God of my praise! For wicked and deceitful mouths are opened against me, speaking against me with lying tongues. They encircle me with words of hate, and attack me without cause. In return for my love they accuse me, but I give myself to prayer. So they reward me evil for good, and hatred for my love.

Appoint a wicked man against him; let an accuser stand at his right hand. When he is tried, let him come forth guilty; let his prayer be counted as sin! May his days be few; may another take his office!

(Psalm 109:1-8 ESV)

And so the 120 Christians who are gathered together in prayer cast lots to appoint Matthias.

This scene, in light of the later appointment of Paul, is an unusual one. Was it wrong that the believers there should look for another apostle on their own? After all, it is clear that God chose Paul later as 12th. So what then are we to make of Matthias’s apostolic appointment?

First, we should note that Peter’s suggestion is rooted in Scripture. Many Psalms, though applicable to David’s life, also contained Messianic prophecy. So it is not at all a leap to suggest that this particular passage (which does, at the least, certainly apply to Judas) should guide the believers. They’re not extracting a passage out of its context; rather, they’re referring to applicable portions of the Word of God for guidance.

Next, we see how they went about the selection process:

So one of the men who have accompanied us during all the time that the Lord Jesus went in and out among us, beginning from the baptism of John until the day when he was taken up from us—one of these men must become with us a witness to his resurrection.” And they put forward two, Joseph called Barsabbas, who was also called Justus, and Matthias. And they prayed and said, “You, Lord, who know the hearts of all, show which one of these two you have chosen to take the place in this ministry and apostleship from which Judas turned aside to go to his own place.” And they cast lots for them, and the lot fell on Matthias, and he was numbered with the eleven apostles.

(Acts 1:21-26 ESV)

They do clearly understand the purpose of the apostolic position: to bear witness to the work of Christ Jesus. So the one they appoint must himself have witnessed Jesus’s Lordship. This is a careful understanding of the role which Christ had himself given to the apostles.

They also pray. They appeal to God for guidance. This is not simply a bureaucratic meeting to determine the “next man up” for a suddenly-vacant job; this is selection of someone who will guide the nascent church according to Christ Jesus’s teachings. So then, Christ Jesus himself must preside and must select a man.

And casting lots was, traditionally, the way to ensure that human intervention was removed from the equation, and that God’s will was instead followed. After all, no man could reasonably (and honestly) control the “randomness” of a lot cast (or, in more modern terms, a dice roll), but God’s sovereignty remained fully in effect – precluding true randomness. The outcome would be by God’s choice and only by God’s choice.

There is, however, some room for contention in that only two men were pre-selected as options for these lots. They “put forward two” rather than choosing from among the whole group.

But it is important to note the significance of this role; the man chosen was to be a leader in the church, and a witness of Christ Jesus’s work. We’ve seen already that simply the requirement of apostleship – having witnessed Jesus – implies a minimum qualification. And a few epistles (though penned later) give high standards for the selection of elders and deacons within local churches. It is then reasonable that a man chosen to be among the 12 apostles, with all their authority and responsibility in the whole church, must be highly qualified and trustworthy.

Having seen these things, it’s clear that the Christians here were acting in obedience to Scripture.

So what then are we to make of Matthias as apostle? We see no more mention of him in the rest of the Bible.

Without knowing the mind of God, we perhaps cannot say. But there are some things we know about God that help to provide some clarity. We know that He is sovereign, so nothing escapes his control – including this selection. We know that He is perfect, and by consequence that he is unchanging, so He did not simply choose incorrectly in the appointment of Matthias, nor did He change his mind.

So then, since the disciples were not acting in disobedience, and God cannot be thwarted, it was indeed in compliance with God’s will that Matthias was appointed, if temporarily, to serve as a 12th apostle. We know that Paul was later appointed by Christ on the road to Damascus, and that he served as “an apostle to the Gentiles” (Romans 11:13, Galatians 2:8)

It is, in a way, perhaps to Matthias’s credit that we don’t hear of him again in Scripture. Had he been rejected by God or apostate, and thus needing replacement by Paul, we would certainly have heard of a man chosen to serve in such an office having fallen into sin. Rather, we can only conclude that since we do not hear from him again, that he served the purpose God would have him to serve in the time God appointed. To be faithful is not always to be known.

So then, Matthias serves as an example to believers today: faithful service does not require recognition, but rather readiness, obedience, and wisdom from the Word of God.

If anyone does not obey what we say in this letter, take note of that person, and have nothing to...

Mon, 16 Nov 2015 08:10:45 -0500

If anyone does not obey what we say in this letter, take note of that person, and have nothing to do with him, that he may be ashamed. Do not regard him as an enemy, but warn him as a brother.

(2 Thessalonians 3:13-15 ESV)

These commands for dealing with a disobedient brother seem contradictory; to “have nothing to do with him, that he may be ashamed” seems like how we might “regard…an enemy” rather than a brother.

It seems cold or uncaring to us to avoid a wayward brother. After all, we tend to avoid our enemies, because we don’t want to be near them, rather than our friends. Isolation (albeit extreme isolation) is kept even today as a more intense punishment for particularly troublesome prisoners.

But in both cases – both in this command and in the modern penal practice – the purpose is the same: to strongly discourage wrong behavior and to immediately cut off opportunity for its continuation. Leaving the brother for a time is intended to send a clear message that the behavior they are currently pursuing is not to be encouraged, nor to be simply tolerated. This is especially true of “busybodies”, against whom Paul warned specifically earlier in the same chapter (in verse 11). To continue in fellowship with a “busybody” – one who gossips to others’ harm – is to provide ample opportunity for the continuation of their sin.

So then it is not in coldness nor in ambivalence that believers are to “have nothing to do with” such a wayward fellow Christian, but with warning and from a desire to see the sin ceased and their obedience restored.

This is evidence of the righteous judgment of God, that you may be considered worthy of the...

Sat, 14 Nov 2015 13:27:53 -0500

This is evidence of the righteous judgment of God, that you may be considered worthy of the kingdom of God, for which you are also suffering—since indeed God considers it just to repay with affliction those who afflict you, and to grant relief to you who are afflicted as well as to us, when the Lord Jesus is revealed from heaven with his mighty angels in flaming fire, inflicting vengeance on those who do not know God and on those who do not obey the gospel of our Lord Jesus. They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might, when he comes on that day to be glorified in his saints, and to be marveled at among all who have believed, because our testimony to you was believed.

(2 Thessalonians 1:5-10 ESV)

Paul encourages the Thessalonian church, who were (like many churches) facing persecution from a world opposed to Christ Jesus, that their suffering was “evidence of the righteous judgment of God, that [they] may be considered worthy of the kingdom of God”.

He then expounds some on God’s judgment, and how God “considers it just to repay with affliction those who afflict you, and to grant relief to you who are afflicted as well as to us, when the Lord Jesus is revealed from heaven…”

We see that those whom God repay] with affliction also “will suffer the punishment of eternal destruction” for their opposition to God.

With this end in mind, how can we possibly seek our own vengeance? How can we not rely on God’s just judgment, and how can we not pity those whose own rebellion has earned them a torment unimaginable and eternal? Such a perspective – one of trusting righteous God and pitying sinful man – ought to drain us of indignant anger, and instead drive us to preach salvation and repentance to those who do wrong us.

It’s a hard perspective to keep, certainly; when we are offended, we (or at least I) tend to act from incensed emotion rather than a mind grounded in God’s truth. So all the more we must study God’s Word, making it to permeate it in our minds, and we must pray to Christ Jesus to make us more like himself.

And then we must discipline our thoughts to remember that our calling is not one of seeking our own victory, but of declaring God’s.

Therefore when we could bear it no longer, we were willing to be left behind at Athens alone, and...

Tue, 10 Nov 2015 06:06:01 -0500

Therefore when we could bear it no longer, we were willing to be left behind at Athens alone, and we sent Timothy, our brother and God’s coworker in the gospel of Christ, to establish and exhort you in your faith, that no one be moved by these afflictions. For you yourselves know that we are destined for this. For when we were with you, we kept telling you beforehand that we were to suffer affliction, just as it has come to pass, and just as you know. For this reason, when I could bear it no longer, I sent to learn about your faith, for fear that somehow the tempter had tempted you and our labor would be in vain.

(1 Thessalonians 3:1-5 ESV)

This is a profound statement of purpose and consequent priorities: Paul says that he and his companions knew that they “were to suffer affliction”, yet the continued in their course of preaching the gospel. Their purpose was as ours is today: not to pursue comfort or happiness, but to faithfully proclaim the truth of man’s sin and Christ Jesus’s salvation. So then, any affliction that must come from serving that purpose is unavoidable, since there is no other course available but to continue in preaching.

Furthermore, we see when that affliction comes, Paul’s thoughts are not on how best to escape it, but on the faith of those whom he has already taught, and whether their faith has flourished or faltered. This again speaks to right Christian priorities: our lives are not our own, but are opportunity for service to the Lord of Truth, and to declare His goodness among a world in need.

And we also thank God constantly for this, that when you received the word of God, which you...

Thu, 05 Nov 2015 06:27:51 -0500

And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers. For you, brothers, became imitators of the churches of God in Christ Jesus that are in Judea. For you suffered the same things from your own countrymen as they did from the Jews, who killed both the Lord Jesus and the prophets, and drove us out, and displease God and oppose all mankind by hindering us from speaking to the Gentiles that they might be saved—so as always to fill up the measure of their sins. But wrath has come upon them at last!

(1 Thessalonians 2:13-16 ESV)

Paul praises God because the Thessalonian church “accepted [the word of God] not as the word of men but as what it really is, the word of God.” This is a cause for rejoicing in evangelism: when the hearers accept the truth you preach not because of your presentation, nor necessarily because of your personal trustworthiness, but because of the Holy Spirit’s revelation to them of the divine veracity of its message.

And the work of the Holy Spirit to establish such a certainty is evident in how the Thessalonian converts responded to the persecution that followed: facing exile and death and isolation, they remained faithful to Christ.

Such should be our firmness in the truth of Scripture: rightly understanding its value as the revealed word of the God, who rules over all, no force on earth should ever be able to sway us from it.

For you yourselves know, brothers, that our coming to you was not in vain. But though we had...

Tue, 03 Nov 2015 06:05:25 -0500

For you yourselves know, brothers, that our coming to you was not in vain. But though we had already suffered and been shamefully treated at Philippi, as you know, we had boldness in our God to declare to you the gospel of God in the midst of much conflict. For our appeal does not spring from error or impurity or any attempt to deceive, but just as we have been approved by God to be entrusted with the gospel, so we speak, not to please man, but to please God who tests our hearts.

(1 Thessalonians 2:1-4 ESV)

Paul writes to the Thessalonian church after he and Timothy were incarcerated and then kicked out from Philippi – as Paul puts it, they “suffered” and were “shamefully treated”.

And yet, he remains confident in the Gospel, unshaken by the world’s harsh reaction. They continue to have “boldness in our God to declare to [the Thessalonians] the gospel of God in the midst of much conflict.” The reason, Paul points out, is because their confidence isn’t based on an assurance or a likelihood of eliciting a favorable response from men. They don’t preach the Gospel because it appeals to the world – that is, “not to please man” – but because they are servants of God, and must “please [Him] who tests our hearts.”

This same truth holds today; our call to preach the Gospel may be beneficial to those who hear, but it is not primarily driven by human response. If it were, we would be right to look on so many missionaries who saw few converts as abject failures rather than as faithful servants. Rather, our call is to obedience to our King, heralding his victory no matter how the world responds.

This is the heart of evangelism: not that we persuade or curry favor with fallen humanity so that we may somehow convince them of truth, but that we declare aloud the triumphant, unfathomable work which our Savior has done for us. Evangelism is not a feat of salesmanship, but an expression of gratitude.

After listing several of the Hebrew patriarchs, and how they lived “by faith”, the...

Tue, 27 Oct 2015 06:14:56 -0400

After listing several of the Hebrew patriarchs, and how they lived “by faith”, the author of Hebrews summarizes them thus:

These all died in faith, not having received the things promised, but having seen them and greeted them from afar, and having acknowledged that they were strangers and exiles on the earth. For people who speak thus make it clear that they are seeking a homeland. If they had been thinking of that land from which they had gone out, they would have had opportunity to return. But as it is, they desire a better country, that is, a heavenly one. Therefore God is not ashamed to be called their God, for he has prepared for them a city.

(Hebrews 11:13-16 ESV)

Though Abraham saw children, though Abel saw God’s pleasure, and though Noah saw God’s protection and God’s judgment, this passage says that all of these Biblical-heroic figures “died in faith, not having received the things promised, but having seen them and greeted them from afar”.

This is not the sort of faith we so often have or even want to have: the sort where we have faith that God will provide for us, or that God will bring us through some trial. That sort of faith looks forward by confidence in God, yes, but it looks very near-forward. It’s a kind of faith that God will “re-stabilize” our lives, rather than faith that whatever God does with our lives is right.

Abraham’s faith was not that God would fill the earth with his descendants during his lifetime, but that what God promised was right, no matter how odd the command. Move to Canaan? Sure. Sacrifice Isaac, your only son? If God has commanded it, it is right.

And Noah’s faith was not only that God would vindicate him over all the mockers who surrounded the ark, but that God’s judgment was justified by His own perfect standards. It takes quite a lot of faith to see all humanity except your own family eradicated, and still to praise God for his perfect judgment.

These people listed had faith not in what God would do, but in God himself. They didn’t simply trust that God would “make it better”; rather, they trusted God that whatever He does is best.

These people “make it clear that they are seeking a homeland”, a land where the presence of God shines forth clearly from his throne, a place distinct from our lives on earth. Their focus was not simply on enduring or making more comfortable their earthly lives, but on being at the last reunited with God Himself.

In the days of his flesh, Jesus offered up prayers and supplications, with loud cries and tears,...

Thu, 22 Oct 2015 09:37:38 -0400

In the days of his flesh, Jesus offered up prayers and supplications, with loud cries and tears, to him who was able to save him from death, and he was heard because of his reverence. Although he was a son, he learned obedience through what he suffered. And being made perfect, he became the source of eternal salvation to all who obey him, being designated by God a high priest after the order of Melchizedek.

(Hebrews 5:7-10 ESV)

Jesus, though he was fully God, here is said to have “learned obedience through what he suffered.”

In the garden of Gethsemene, Jesus “offered up prayers and supplications, with loud cries and tears, to him who was able to save him from death.” And we’re told that “he was heard because of his reverence.”

Yet God didn’t “let [the] cup [of God’s wrath] pass from [him]” (Matthew 26:39 ESV). Christ prayed in full submission:

And going a little farther he fell on his face and prayed, saying, “My Father, if it be possible, let this cup pass from me; nevertheless, not as I will, but as you will.”

(Matthew 26:39 ESV)

This is the profound depth of obedience that Jesus the Son gave to the Father: that he would be tried unjustly by men, executed in the cruelest way mankind knew at the time, and worst of all, bear the immeasurable weight of the full wrath of God against all the sin of His own people.

But we see here that Jesus already demonstrates the willing submission of obedience, and we know that as sinless God incarnate, Jesus the Son already knew perfect obedience to the Father. So then what does it mean to say that he learned obedience?

A look at the original text yields Strong’s Greek word 3129 – manthanó, which means to learn in the sense either of being instructed or of understanding from experience.

By the instruction of the Father, Jesus’s obedience was fulfilled by the experience of the ultimate willing submission, even to death. Christ, as fully God, was not lacking in any knowledge. Indeed, all three persons of the Trinity are perfectly omniscient. Rather, by subduing his desire (to avoid the full cup of God’s wrath) to that of the Father, Jesus made active his ongoing obedience, performing an act of willing submission. Matthew Henry explains:

Christ made improvement by his sufferings. By his passive obedience, he learned active obedience; that is, he practiced that great lesson, and made it appear that he was well and perfectly learned in it; though he never was disobedient, yet he never performed such an act of obedience as when he became obedient to death, even to the death of the cross. Here he has left us an example, that we should learn by all our afflictions a humble obedience to the will of God. We need affliction, to teach us submission.

In this intense suffering, Jesus made manifest the perfect obedience he had – and has – to God the Father.

And through this obedience, Christ atoned for our sins and set an example for those he redeemed. We Christians – the ones to whom Christ has given his name – must likewise be always ready to submit our own desires and wills to the perfect will of God. Who among us can claim that the obedience required of us is a magnitude rivaling that required of Christ in enduring history’s most intense suffering? And by that suffering, we see God’s perfect will accomplished to a profound depth of mercy towards us all. How then could we possibly doubt the perfection of his will in all that he commands for us?

Let us therefore strive to enter that rest, so that no one may fall by the same sort of...

Fri, 16 Oct 2015 08:46:52 -0400

Let us therefore strive to enter that rest, so that no one may fall by the same sort of disobedience. For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart. And no creature is hidden from his sight, but all are naked and exposed to the eyes of him to whom we must give account.

Since then we have a great high priest who has passed through the heavens, Jesus, the Son of God, let us hold fast our confession. For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin. Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need.

(Hebrews 4:11-16 ESV)

In order to enter God’s rest – heaven – we must be without sin. And completely without sin, because Christ knows all of our sins, and his word “[discerns] the thoughts and intentions of the heart.”

But praise to God, because “we have a great high priest who has passed through the heavens, Jesus, the Son of God”, who as high priest atones for the sins of his people. So then, “let us hold fast to our confession”, unwaveringly assured of the sacrificial work of redemption He has accomplished.

And by His power – thanks to Christ! – we can “with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need.”

For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the...

Mon, 12 Oct 2015 15:23:46 -0400

For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him, and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name, king of righteousness, and then he is also king of Salem, that is, king of peace. He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling the Son of God he continues a priest forever.

See how great this man was to whom Abraham the patriarch gave a tenth of the spoils! And those descendants of Levi who receive the priestly office have a commandment in the law to take tithes from the people, that is, from their brothers, though these also are descended from Abraham. But this man who does not have his descent from them received tithes from Abraham and blessed him who had the promises. It is beyond dispute that the inferior is blessed by the superior. In the one case tithes are received by mortal men, but in the other case, by one of whom it is testified that he lives. One might even say that Levi himself, who receives tithes, paid tithes through Abraham, for he was still in the loins of his ancestor when Melchizedek met him.

(Hebrews 7:1-10 ESV)

There is much discussion made of whether Melchizedek was an early incarnation or appearance of God in humanlike form. The author of Hebrews points out rightly that there are certainly some parallels between Melchizedek’s titles and role and Christ’s.

But the more key point to which the author here draws focus is the insufficiency of even Abraham, the patriarch by whom the Hebrew nation claimed their covenantal position as God’s people. It is clear here that Abraham recognized a superiority and a priesthood in this man who is “without…genealogy”, and thus is outside the nation of Israel.

To a Hebrew audience, this was at the least a challenging concept. How could it be that the Levitical priesthood, appointed by God in Jewish law, was somehow insufficient?

Of course, the issue here is an understanding of goals; the role of the priests were to worship God, to teach the nation of Israel, and to aid in obedience to the specific instructions God had laid out as symbols of his relationship with Israel. The priests, then, were not a means of attaining perfection:

Now if perfection had been attainable through the Levitical priesthood (for under it the people received the law), what further need would there have been for another priest to arise after the order of Melchizedek, rather than one named after the order of Aaron?

(Hebrews 7:11 ESV)

The simple fact that another of this superior breed of priest was required demonstrated the insufficiency of the Levitical priesthood while also providing a means of attaining perfection unencumbered by the flawed obedience of human priests.

Jesus is, as the author points out, “the guarantor of a better covenant” (v22).

Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these...

Thu, 08 Oct 2015 05:58:02 -0400

Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world. He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power.

(Hebrews 1:1-3 ESV)

The word here translated as “exact imprint” is the Greek charakter – yes, from which we get “character”. Jesus is the character of God, an “exact expression” or “exact reproduction.” Jesus has the full nature of God.

This was an important point to make to Hebrew readers, who cherished the words of what we now call the Old Testament. They read with eagerness about the ways that God spoke to their ancestors about His own character. Paul now tells them to seek out with equal excitement the incarnate revelation that God now gives; rather than merely speaking about himself, he has now – in Christ – perfectly demonstrated his character.