Short answers, pulled from the story.
The term free will, or liberum arbitrium, was introduced by Christian philosophy in the 4th century CE. This theological framework established that the will is free if it does not have to be such as it is. This requirement was universally embraced by both sides of the debate until the Enlightenment proposed new meanings.
The Stoic philosopher Chrysippus argued that human actions are determined by prior causes yet still compatible with a form of freedom. Aristotle and Epictetus developed the notion of compatibilist free will in the 4th century BCE and 1st century CE respectively. They suggested that control exists as long as nothing hinders us from doing or choosing something.
The thought experiment of Laplace's demon illustrates the concept of causal determinism where everything is caused by prior conditions. This entity knows all facts about the past and present and all natural laws, allowing it to foresee the future down to the smallest detail. If the laws of nature are determinate, then the present state of the universe is the effect of its antecedent state.
Hard determinists like Paul Henri Thiry Baron d'Holbach argue that determinism is true and incompatible with free will. They claim that free will does not exist and view humans as mechanical things whose behavior is entirely determined by prior events. This perspective suggests that the feeling of freedom is an illusion arising because we are conscious of our actions but unconscious of the causes that determine them.
Metaphysical libertarianism posits that determinism is false and that free will is possible. This view requires that the agent be able to take more than one possible course of action under a given set of circumstances. Philosophers like Robert Kane and Peter van Inwagen argue that indeterminism provides the necessary elbow room for free will.
Experiments by Benjamin Libet and others have shown that brain activity precedes conscious awareness of a decision. This finding leads some to argue that free will is an illusion. The neuroscience of free will suggests that the brain's activity is governed by physical laws and that conscious volition may be an epiphenomenon of neural processes.