I am means I am not, for to be one thing thou cannot be another. I am here means I am not there.
Working from here, we wonder what I am, in the purest sense, then means. I am, emphatically, which must mean there are parts which I am not.
What am I not?
I am not a woman.
I am not dead.
I am not. . .
Those are all instances of what I am not, but to be, to say I am, I need say no more. When I say I am not, the fact that I say, means I exist, means I am, and therefore some qualifier proceeds. I am not (fill in the blank.) I am not, without something following, is nonsense.
Above is my poor defense of free will, but Dr. Peterson probably did a, better is obvious, an actually good job.