The blind man’s cane. Ask where the man stops. Not philosophically — practically, in the way a surgeon would need to know. He does not feel the cane in his hand; he feels the kerb, at the far end of it, through a rod of ash he is not aware of holding.

The boundary has moved to the tip. It moves back when he sets the cane down, and it moves to the front bumper when he is parking a car, and it moves to the cursor within about four hundred milliseconds of picking up a mouse, and it moved to the edge of the flint about two and a half million years ago and has never returned to the skin since.

An enhancement adds capability to a bounded system. That is what the word means. It requires the boundary as a precondition.

There is no boundary. There has not been one within the period for which the word human has had a referent. So the transhuman is not an ambition that is difficult, or distant, or dangerous. It is an ambition that is ungrammatical — it takes an object that the language cannot supply.

You cannot go beyond the human. Not because it is sacred. Because it does not have an edge to go beyond.