Thomas Aquinas, Compendium of Theology

This suggests what we ought to think of fate. Many effects are found to occur haphazard if they are regarded from the standpoint of secondary causes. Some thinkers are unwilling to refer such effects to a higher cause that ordains them. In consequence, they must utterly reject fate. On the other hand, others have desired to trace back these seemingly accidental and fortuitous effects to a higher cause that plans them. But, failing to rise above the order of corporeal entities, they attributed such devising to the highest bodies, namely, the heavenly bodies. And so they contended that fate is a force deriving from the position of the stars, and that this accounts for happenings of this kind. But we showed above that the intellect and will, which are the true principles of human acts, are not in any proper sense subject to heavenly bodies. Hence we cannot maintain that events which seemingly occur at random and by chance in human affairs, are to be referred to heavenly bodies as to the cause that charts them.

There seems to be no place for fate except in human affairs, in which hazard has a part to play. It is only about such events that men are accustomed to inquire in their craving to know the future, and it is also about these that an answer is usually given by fortunetellers. Hence fate (fatum) is a word formed from the Latin verb fari, to foretell. To acknowledge fate thus understood is opposed to faith. Since, however, not only natural things but also human affairs are under divine providence, those events that seem to happen at random in men's lives must be referred to the ordination of divine providence. Consequently those who hold that all things are subject to divine providence, must admit the existence of fate. Fate taken in this sense is related to divine providence as a real effect of the latter. For it is an explanation of divine providence as applied to things, and is in agreement with the definition given by Boethius, who says that fate is a "disposition," that is, an unchangeable ordination, "inherent in changeable things."

Yet, since we ought not to have even words in common with infidels, so far as possible, lest an occasion for going astray be taken by those who do not understand, it is more prudent for the faithful to abstain from the word "fate," for the reason that fate is more properly and generally used in the first sense. Therefore Augustine says that if anyone believes in the existence of fate in the second sense, he may keep to his opinion but should correct his language.