Imagine a ball rolling down a pipe. Att one point the pipe forks, and at that point there is a simple mecanical device that sorts the balls according to size: all balls larger than 4 cm in diameter go left, all smaller ones go right. Let this be the definition of a "choice" (with the device as the agent) for the following argument, and let "you" define a certain arangement of atoms in Eliezers block-universe-with-glue. Then "you" will be what "decides" every time you make a choice; trivially so, given those definitions.

My question is, what other definitions could we use to reach a different conclution?

I mean, if you define "free" in "free will" as "not goverend by physics", or "you" as different from the (or some part of the) structure of your atoms, we are having a different debate here.