"And what about this? Who would do a finer job, one man practicing many arts, or one man one art?"
"One man, one art," he said.
"And, further, it's also plain, I suppose, that if a man lets the crucial moment (kairos) in any work pass, it is completely ruined."
"Yes, it is plain."
It is this neglect of the crucial moment, due to the interruption of a work, which I would like to put forward as a Platonic cousin of the 'Aristotelian' cousin of the deviance from a terminus ad quem. (Aristotelian is in scare quotes here not because I am aware of any divergence from Aristotle's doctrine on this point in the late Aristotelians, but simply because I am not yet aware of Aristotle's doctrine on this point, if he has one. I suspect it is not too different from Plato's in any case.)
I don't have a great quote for terminus ad quem but "J" proposes a squirrel eating an acorn, preventing its arrival at becoming an oak. The squirrel is of course only fulfilling its own being--nothing "devilish" about that.