Freedom and the Moral Law
Are we free to do everything we want to do physically? On a practical level, unless we have a physical handicap, we enjoy a degree of freedom of movement. We are able to move our heads, to raise fingers, to run, etc. But this physical freedom isn't unlimited. For example, while we can flap our arms, we can't fly. Our freedom of movement is governed by rules which we are unable to violate. We can't live without eating, just as we can't eat just anything we want. To rebel against the limits of our physical liberty is useless. We are forced to submit ourselves to the laws of nature.
Are we free to do everything we want to do psychologically? Our thought and our will possess a certain degree of freedom as well. You can imprison someone for not believing in a political ideology, beat him, torture him, but you cannot prevent him from thinking how much he detests your political ideology, or of wanting to overthrow your rule. You can prevent him from expressing his thoughts by force, but one cannot force him to change his opinion; he keeps his freedom of thought.