The trouble begins the moment you take physics seriously. Every event we have ever examined has a cause; the movements of matter, including the electrochemical activity of a human brain, appear to follow from earlier states of the world plus the laws of nature. If that is true all the way down, then the state of the universe a thousand years before your birth, together with the laws, already fixed everything you would ever "decide." The feeling of an open future would be exactly that — a feeling.
This is hard determinism: the conjunction of two claims — that determinism is true, and that determinism rules out free will. Its defenders argue we should follow the reasoning wherever it leads, even to the unsettling conclusion that praise, blame, and desert need rethinking from the ground up.
The libertarian replySomething in us begins.
The libertarian about free will refuses the first domino. On this view we are, at least sometimes, genuine originators of our actions — a choice can be truly up to us in a way not settled by the prior state of the world. Kant argued that morality itself presupposes this freedom: an "ought" makes no sense if we could never have done otherwise. The cost is metaphysical. Libertarians must explain how an undetermined choice is still ours and not merely random, since a coin-flip in the brain is not obviously freer than a domino.
The compatibilist turnRedefining the word free.
Most philosophers today take a third path. Compatibilism argues the whole dilemma rests on a bad definition. Freedom, said Hume, was never the absence of causation — it was the absence of compulsion. A person who acts from their own desires, deliberations, and character is free, even if those desires themselves have causes. The prisoner is unfree; the person choosing tea over coffee is free — and the difference has nothing to do with whether physics is deterministic.
Harry Frankfurt sharpened this with a famous example: what matters is whether you endorse your own motives — whether the desires you act on are ones you want to have. A person dragged by an addiction they hate is unfree; a person acting on desires they reflectively affirm is free, causation notwithstanding. Critics answer that this redefines the prize rather than winning it: if the whole chain of causes was fixed in advance, calling the last link "yours" may be relabelling, not liberation.
Notice what the debate really turns on: not a fact about the world so much as the meaning of a single word. Decide what "free" must mean, and your answer to the whole question tends to follow.