It’s a climactic moment in a thrilling pericope.

Jesus has just grabbed Peter from the waters, waters he was just walking on top of going towards Jesus but then, upon seeing the wind and waves, he started to sink. His cry of “Lord, save me,” is as programmatic for the Gospel of Matthew as is what he asks Jesus, “If it is you, command me to come toward you.”

Jesus stretches out a hand, grabs the sinking disciple, deposits him in the boat, and asks what appears to be a question with an obvious answer: “O you of little faith, why did you doubt?”

Let’s take a quick dip into that question: why does Jesus ask why? More pointedly, what significance is there in the type of why question Jesus uses?

If you’re just interested in why this might matter for interpreting our pericope at hand, and not all the explanation, skip to the end–the Greek comes first on this site.

How to ask why

Matthew uses 3 of the common ways in Greek to ask the question “why?”[1]

  1. τί: 6.28; 7.3; 16.8; 17.10; 19.7, 17; 20.6; 22.19; 26.10)[2]
  2. διὰ τί (7x: Matt. 9:11, 14; 13:10; 15:2-3; 17:19; 21:25)
  3. εἰς τί (2x: 14.30, 26.8

Of these three phrases, the one in question in our passage is εἰς τί;

What does ‘why’ mean?

Why have so many ways to ask “why”?

It turns out, they are not identical in meaning. Here’s one of those instances where Greek’s famed (and often over-hyped) specificity really delivers. A plain τί is possible—and a quite ancient—way to ask “why?” As such, we expect there to be some sort of nuance in a more specific construction which uses one of these prepositional phrase versions of the question “why?”

The esteemed A. T. Robertson summarizes the lay of the land:

“There is very little difference between τί= ‘why’ and διὰ τί= ‘because of what’…But purpose again is expressed by εἰς τί.” (739) (compare also BDF 299(4)

Let’s look at a couple examples to see the differences in action:

  • (1) τότε προσελθόντες οἱ μαθηταὶ τῷ Ἰησοῦ κατ’ ἰδίαν εἶπον διὰ τί ἡμεῖς οὐκ ἠδυνήθημεν ἐκβαλεῖν αὐτό;  (Mt 17.9)
  • At that time the disciples, having approached Jesus privately, said: “Why [=on account of what] were we not able to drive it [the demon] out?”

Compare this to:

  • (2) ἰδόντες δὲ οἱ μαθηταὶ ἠγανάκτησαν λέγοντες· εἰς τί ἡ ἀπώλεια αὕτη; (Mt. 26.8)
  • Now seeing [these things] the disciples became angry, saying, “why [=for what purpose] is this waste?”

In example (1), the disciples use διὰ τί; In the flow of the situation, we see that they are looking for an explanation. They want to know the factors behind the surprising outcome that this demon, contrary to the others they have cast out, did not yield to them. Thus, their question is something like, “What are the factors that explain why we were unable to drive the demon out?”

Example (2) is also a ‘why’ question, but with εἰς τί. Here a different nuance comes to the fore. The disciples are asking about the usage (‘waste’) of an expensive jar of ointment. But they aren’t inquiring about the factors that led up to the jar of expensive perfume being broken open. That is common knowledge to everyone who just watched it happen. Instead, they want to know what the aim animating the actions was. In other words, “What is the aim behind this waste [of the expensive perfume]?”

Throughout, Matthew is consistent in maintaining a distinction in meaning between these two different questions. “Why” is an appropriate English translation for both, but they focus on different nuances:

  • εἰς τί; What is the aim?
  • διὰ τί; What are the factors that undergird it?

With a handle on the distinction, let’s return to poor Peter in the boat and ponder what Jesus’ question is getting at.

What does Jesus’ ‘why?’ mean?

Jesus asks question εἰς τί…;, which is an inquiry after a purpose/aim. In other words, he asks “for what purpose/aim did you doubt?”

There is no great mystery what factors led to Peter’s struggle with doubt:

  • there’s a storm
  • big waves driven by fierce wind
  • he’s been up all night rowing and is tired
  • oh, and he’s walking on top of water, which is supposed to happen

But Jesus doesn’t ask about that. That would be a διὰ τί question. Instead, Jesus presses Peter to answer what his aim was.

It’s as though he asks: Peter, what did you possibly hope to gain through doubt that you weren’t already gaining by faith?

This is fertile ground to till in when considering Matthew’s larger theology of discipleship. And the seed from which it grows is a simple Greek question: “why?”

[1] There are more possibilities in Greek. A common 4th version is the phrase ἵνα τί, but that does not appear in Matthew.

[2] Τί appears 68 times, only the 9 above of which are “why” instead of “what.” Numbers come from an NA28 Accordance Syntax search for “τί”