Short answers, pulled from the story.
Free will is the capacity to choose between different possible courses of action, exercise control over one's actions in a way necessary for moral responsibility, or be the ultimate originator of one's actions. Philosophers disagree on whether such freedom is compatible with determinism, divine foreknowledge, or other constraints.
Incompatibilism holds that free will and determinism cannot both be true; incompatibilists either reject free will (hard determinism) or reject determinism (metaphysical libertarianism). Compatibilists, by contrast, hold that free will is consistent with determinism, defining freedom as the absence of external coercion or compulsion rather than escape from natural law.
The compatibilist view of free will has been attributed to Aristotle in the 4th century BCE and Epictetus in the 1st century CE. The incompatibilist view is traced by scholar Susanne Bobzien to Alexander of Aphrodisias in the 3rd century CE. The Latin term liberum arbitrium entered the vocabulary through Christian philosophy in the 4th century CE.
The consequence argument, formulated by Carl Ginet in the 1960s, holds that if determinism is true, we have no control over past events or the laws of nature, and therefore no control over our present choices, which are their necessary consequences. Peter van Inwagen noted that C. D. Broad had a version of this argument as early as the 1930s.
Theological determinism holds that all events are predestined or foreknown by an omniscient deity. Strong theological determinism claims a creator deity dictates all events outright, eliminating libertarian free will entirely. Weak theological determinism holds that divine foreknowledge alone makes the future inevitable; thinkers such as Boethius, Thomas Aquinas, and C. S. Lewis argued this is compatible with human freedom by appealing to God's non-temporal knowledge.
Schopenhauer argued in The World as Will and Representation that human actions as phenomena are subject to necessity, so free will in the conventional sense does not exist. In On the Freedom of the Will he stated that while one can do what one wills, in any given moment one can will only one definite thing. He held that the will as a thing-in-itself, outside time and space, is groundless and thus free, but the individual person as a phenomenon of the will is not.