Oh, no, I messed that up.
He says, “Take heart; it is I; do not be afraid.”
I love this self-introduction. I want to go to my friend's house and when she goes to get the mail, bound out of the bushes, "Take heart; it is I!" I want to subject the UPS man to it, the grocer, my boss. I can see the UPS man jump out of his shorts pleated like slacks (Really?! What’s the point? They’re still shorts!), "Hot dang!” He shouts, “All the crazies are on my route!"
The statement is ludicrous because of it's arrogance. "Take courage! I'm here!" Unless . . . well . . . unless it’s sufficient reason take courage.
The sentence's construction makes it obvious that, "it is I" is the reason the exhausted, soaked, and generally scared for their lives disciples should "take heart", why they should "not be afraid."
Jesus' logic is not unlike our logic nor does he have a different logic than we do. Those are commonly held and terrifyingly dangerous views in some circles. No, Jesus was employing boring, old-fashioned, run-of-the-mill logic. By His comment, "it is I", I assume the disciples feared the ghost. When He said, "take heart" and "do not be afraid", Jesus was recognizing that "I see dead people" is a terrifying state. Jesus is going to give the disciples a logical reason that they need not be afraid.
And it's not just, "Sure, the sea is boiling up and the wind is pounding you into it and sure, you see a ghost, but you don't need to be afraid because it's just me." No, what Jesus says is more like, "Since I can walk on water, and because I'm here, you do not need to be afraid". Okay, Jesus didn't say, "Looky here! I can walk on water!" But any theologian worth his regalia will tell you that, said or unsaid, that was part of the lesson - "I can overcome the natural world." In other words, if all of their circumstances were the same but Jesus, the Water-Walker, were not present, it would be logical to freak out. "However, I'm here; take heart."
Jesus' confidence in His own power and trustworthiness is better aligned with reality than was the disciples'. They're a little deficient in the facts and He's going to supply better facts so that they needn't be afraid: "The benevolent Water-Walker's here”. He's not trying to move them out of “human logic” and move them into “God’s logic”. He's providing them with more truth so that they can experience the emotions that follow this understanding.
I slipped that "benevolent" in there, didn't I? Jesus wouldn't be telling them to "take heart" and "fear not" unless He had 1) power beyond their circumstance and unless He were 2) benevolent enough to use that power for their good.
Even knowing that God, by definition, could not be otherwise than He is, I am compelled to thank him that He is benevolent. I still can imagine a Grand Who-Hah as someone whose presence would imply, "Crawl under a rock; it is I; pee your pants." But Jesus supplies me, through the relation of this event with better facts. He says, "I'm trustworthy. If I were not with you, you would be in danger, but take heart, it is I."