Four-Fold State of Man
In the four-fold state of man (1: before the fall, 2: after the fall, 3: after regeneration, & 4: in glory) man has the liberty of will to make voluntary choices. That means his choices are not forced or coerced to do something he does not want to do. After the fall, while men retain their natural liberty (not coerced), they come under the bondage to sin and thus they lose the willingness/moral ability to choose good. It is important to take note that there is a distinction between liberty and ability. Many stumble here. The will of man has liberty - We are never forced to do something we do not want to do in any of the four states. In that sense our wills are always at liberty. But that is quite different than the ability of the will. The ability of the will to be good or bad is not something that is retained in the fall. We will always, apart from the grace of God, choose what is bad since the fallen man's will and affections are corrupted. We still have the liberty to choose (without coercion) but will choose evil by necessity due to a corruption of nature, and are unable to do otherwise.