equinom's right, and that's in fact how Kant deduced that 2+2=4
There are actually two schools of thought that I know of when it comes to the issue of human free will:
The first, known as determinism, says that human beings have no free will whatsoever and that every action they perform or event that they are involved in is a result of one or more predetermined causes.
The second says that one is free to do as they wish in this world regardless of their fate or as dafox said "God's big plan for them". An action is the result of one's motives and motives are purely under the person's control.
Both these ideas extend out of the principle of causality, which says that for everything there is a cause. Here's an example someone once sent me:
Boiling is a natural phenomenon requiring a cause, in accordance with the principle of causality. We consider the warmth of water as its cause. Like boiling, this warmth requires a prior cause. If we take boiling and warmth as two parts of the chain of existence or of the succession of agents and causes, we find that it is necessary to add to this chain another part; for each of the two parts is in need of a cause. Therefore, they require a third part. Also, the three parts together face the same problem. They need a cause of their existence, since every one of them is subject to the principle of causality. This is constantly and always the case with the chain of cause, even if it includes infinite parts. So, since every part of it requires a cause, the chain as a whole requires a cause. The question 'Why does it exist?' extends as far as the parts of the chain extend. No decisive answer to this question is possible, as long as the succession in the chain does not lead to a part that is self-sufficient and not requiring a cause, so that this part can put an end to the succession and give the chain its first eternal beginning.
I pretty much think that I have free will to do as I please, but sometimes even the simplest of actions can go back along an infinite chain of causes just like the previous example.