Of all the things that happen, the cause is said to be either God, or necessity, or fate, or nature, or chance, or accident. But God’s function has to do with essence and providence: necessity deals with the movement of things that ever keep to the same course: fate with the necessary accomplishment of the things it brings to pass (for fate itself implies necessity): nature with birth, growth, destruction, plants and animals; chance with what is rare and unexpected. For chance is defined as the meeting and concurrence of two causes, originating in choice but bringing to pass something other than what is natural: for example, if a man finds a treasure while digging a ditch: for the man who hid the treasure did not do so that the other might find it, nor did the finder dig with the purpose of finding the treasure: but the former hid it that he might take it away when he wished, and the other’s aim was to dig the ditch: whereas something happened quite different from what both had in view. Accident again deals with casual occurrences that take place among lifeless or irrational things, apart from nature and art. This then is their doctrine. Under which, then, of these categories are we to bring what happens through the agency of man, if indeed man is not the cause and beginning of action? For it would not be right to ascribe to God actions that are sometimes base and unjust: nor may we ascribe these to necessity, for they are not such as ever continue the same: nor to fate, for fate implies not possibility only but necessity: nor to nature, for nature’s province is animals and plants: nor to chance, for the actions of men are not rare and unexpected: nor to accident, for that is used in reference to the casual occurrences that take place in the world of lifeless and irrational things. We are left then with this fact, that the man who acts and makes is himself the author of his own works, and is a creature endowed with free-will.
Further, if man is the author of no action, the faculty of deliberation is quite superfluous for to what purpose could deliberation be put if man is the master of none of his actions? For all deliberation is for the sake of action. But to prove that the fairest and most precious of man’s endowments is quite superfluous would be the height of absurdity. If then man deliberates, he deliberates with a view to action. For all deliberation is with a view to and on account of action.
An Exact Exposition of the Orthodox Faith. Chapter 25 St John Damascene