See also determinism
from... http://www.newadvent.org/cathen/06259a.htm
The question of free will, moral liberty, or the liberum arbitrium of the Schoolmen, ranks amongst the three or four most important philosophical problems of all time. It ramifies into ethics, theology, metaphysics, and psychology. The view adopted in response to it will determine a man's position in regard to the most momentous issues that present themselves to the human mind. On the one hand, does man possess genuine moral freedom, power of real choice, true ability to determine the course of his thoughts and volitions, to decide which motives shall prevail within his mind, to modify and mould his own character? Or, on the other, are man's thoughts and volitions, his character and external actions, all merely the inevitable outcome of his circumstances? Are they all inexorably predetermined in every detail along rigid lines by events of the past, over which he himself has had no sort of control? This is the real import of the free-will problem.