Mathematical calculations are irrespective of time: they deal with the 'essences of things,' which are timeless, as Aristotle says of the relation of the diagonal to the side of the square: time makes no difference in that relation. But when an engineer comes to apply such calculations to practical work, he re-enters upon considerations of time and place. The affirmative and negative judgements spoken of in the text make accidental propositions: now accidental propositions involve time, e.g., 'there stood a lion in the way': essential propositions do not, e.g., 'a lion is an animal of the cat tribe.'

Of God and His Creatures: 2.96