You Are what you Learn
Determinism
Some determinist conclude the following:
Bob currently works at job A and gets an offer to work at job B. He now has a "choice" to stay at job A or switch to job B. Some determinists will say that Bob doesn’t really have a choice, it’s already determined, and if Bob were to deliberate between both options, he’s only fooling himself into thinking he could choose one or the other.
Same Word, Different Subjects
Say I have a card with a word printed on it. I show it to a French speaker and they do one thing. I show it to a German speaker and they do something else. (Because the word has different meanings in the different languages.) If the word "caused" the French speaker to do something, why did it cause the German speaker to do something else.
The difference is that the speakers were actively involved in deciding what to do. They interpreted the word. They actually decided what to do. The word prompted them, but didn't by itself cause them. Sure, everything is determined: someone ultimately taught them the language, however the result of that learning IS the person. You are that thing that is constructed by all your learning.
Indeed, the circuitry in the brain determines what you do, but you ARE that circuitry in the brain.
Another way of saying this is: remove the brain from the French speaker, and then show them the card, and you can bet they will NOT do the same thing as if they had a brain. The brain is a very important part of why people do things, and that wiring of the brain is YOU.
Same Word, Different Time
There is more evidence in how you personally affect what happens even when everything is determined, and that is when you behave in a different way to the same prompt.
As an example, consider being told to clean out a closet. You are asked one time in the morning when you are fresh, you have no particular plans for the day, and you know you will have visitors next week. The other time you are asked is late a night, after a strenuous day, and you have an important meeting the next morning.
It is the same prompt. It is the same work to be done. But chances are very slim that you will do it late at night, and the reasons are obvious. My point is only that the message closet does not force a single determined outcome, but that in fact the outcome is determined by your mood, energy level, and plans for the immediate future. That is YOU. You really do determined what you do.
Of course, no one would expect you to clean out a closet late at night before an important meeting. So you could say that is determined as well. But my point is that the thing that does the determining is YOU. It makes sense to put off the cleaning until a more appropriate time, because you actually exist and actually participate in the determination of what should be done.
The Essense of You
I want to be clear about two meanings of "you". Clearly I can point to your body, and say that is you. That is entirely correct.
However there is another sense of you, which is the animus of your body. It is your personality. It is the special way you interact with people. Perhapse the running joke you have with one person, or the shared love of a particular piece of music. Lets call this the "spirit you" because it is the active process that runs in your body, and if you body died, the spirit you would simply no longer be there.
The spirit you comes from the way your nerves are wired. When you learn, your brain wires nerves together in order to remember. Those memories then drive future behavior. It is no surprise that your behavior comes from your memories. Clearly you can only act on what you know, and that is memories.