I need to reformat this entire thing because I've changed my mind on same of these arguments. I'm going to drop the "I have free will" part from my argument and progress without it. My belief in free will has waned and this is quite a big assumption in the argument that is not needed. I will leave everything else up, though, for you to read it. Not too much will change, but a point of the argument will.
You can read my current thoughts on free will here.
What do I mean by a set future via omniscience?
If someone or something were able to have a vision of what the future is and can't be wrong about the future, this means that humans are slaves to this vision of the future. If the future includes me eating pizza tomorrow at noon, I have no choice to refrain from pizza eating. No matter how hard I tried to avoid eating the pizza or what other people did to stop me from eating pizza, I'd still have to eat pizza. If God saw a future in which I never ate meat again, I would never be able to eat meat no matter how hard I tried to eat meat. I simply would not have any choice in the matter.
What do I mean by "freedom to make choices?"
In my essay, I use the concepts of freedom, freedom to make choices, and free will interchangibly. I'm well aware that free will (the idea of the ability to freely do anything) is highly restricted, but this isn't what I mean when I discuss freedom. When I discuss freedom, I mean the ability to choose to either do x or not do x at any given time y...such as eating pizza or not eating pizza. If I have the ability to eat pizza or refrain from pizza eating, I have the ability to make a choice. If I don't have the ability to refrain from pizza eating, I have no choice.
God doesn't matter, the future matters...
Many people object and say "God isn't controlling what happens! You're still making choices because God allows you to!" The focus of this argument is not on God, persay, but rather on a set future. I should have modified my essay to make this more clear. If a future is "set," no matter if someone saw it, a God made it or didn't make it, etc, we can't have freedom because we're restricted to making actions in line with such a future.
So, who or what is forcing the future to happen, then?
The problem with identifying what or who actually causes the future to "happen" is difficult because there are some logical contradictions involved. Suppose a future is set in which I never eat meat again. If someone were to place meat in my mouth, would the meat disappear? Would people be forced not to have thoughts about feeding me meat? I don't know. It really doesn't matter, though, for my argument. If the future is set, the future must happen.
My "The Argument" section is flawed.
Andrew pointed out that this section has problems. Unfortunately, I don't know much of what he is talking about because I have't taken formal logic classes yet (I will be doing so next semester). I will attempt to fix this section and better explain my argument using an argument from my philosophy professor who agrees with my conclusion and wrote a journal article and did his dissertation on this topic. Please view his paper here.
Johnson's argument:
Assume that God exists and call whatever action you will perform at noon tomorrow ‘X’.
(1) If you can freely perform X at noon tomorrow, it must be possible for you to not
perform X at noon tomorrow (from the Principle of Alternate Possibilities).
(2) God believed yesterday that you will perform X at noon tomorrow. (This follows
from God’s omniscience).
(3) God’s beliefs are events.
(4) All past events are necessary (the past cannot be undone).
(5) God’s past belief that you will perform X at noon tomorrow is necessary (from 2,
3 & 4).
(6) Necessarily, if God believes something will occur, it will occur. (This follows from
God’s necessary omniscience.)
(7) It is necessary that you will perform X at noon tomorrow (from 5 & 6 by a
‘transfer of necessity’).
(8) It is not possible for you to not perform X at noon tomorrow (from 7).
(9) Therefore, you cannot perform X at noon tomorrow freely (from 1 and 8).
OR
Assume that God exists and call whatever action you will perform at noon tomorrow ‘X’.
(1) If you can freely perform X at noon tomorrow, it must be now-ontologically
possible for you to not perform X at noon tomorrow (from the Principle of
Alternate Possibilities).
(2) It is now-ontologically possible for you to not perform X at noon tomorrow only if
your not performing X at noon tomorrow is not contrary to something that exists
(by definition of ‘ontological possibility’).
(3) God’s past belief that you will perform X at noon tomorrow exists.
(4) God exists and cannot have false beliefs.
(5) It is now-ontologically necessary that, if God believes you will perform X at noon
tomorrow, you will perform X at noon tomorrow (from 4).
(6) Your future performance of X at noon tomorrow exists (from 3 and 5 by the
‘transfer of ontological necessity’).
(7) Your not performing X at noon tomorrow is contrary to something which exists
(from 6).
(8) It is not now-ontologically possible for you to not perform X at noon tomorrow
(from 2 and 7).
(9) Therefore, you cannot freely perform X at noon tomorrow (from 1 and 8).