The theory about freedom that despite what has happened in the past, and given the present state of affairs and ourselves just as they are, we can choose or decide differently than we do – act so as to make the future different. Libertarianism asserts the freedom of the will or origination, and is contrasted with determinism.
Contemporary libertarians cite quantum mechanics as evidence that determinism is false. Even if this is so, the random behavior of atoms certainly does not by itself make for the freedom and moral responsibility asserted by libertarians.
Roy C. Weatherford, “Libertarianism,” The Oxford Companion to Philosophy (Oxford Univ. Press, 1995), 485.