«Then again, because the best way to understand the nature of Plants or Man is to consider in what way they gradually come into existence and are generated from their seeds, we must devise such principles as are the simplest and easiest to know, from which we may demonstrate that the stars, the earth, in short, everything we observe in this visible world, could have arisen as from certain seeds — although we may well know that they never did thus arise. For in this way we shall explain their nature far better than if we were to describe them only as they are now.
I say that we seek principles that are simple and easy to know; for unless they are such, we shall not be in need of them. The only reason why we assign seeds to things is to get to know their nature more easily and, like mathematicians, to ascend from the clearest to the more obscure and from the simplest to the more complex.»

Spinoza, Principles of Cartesian Philosophy, Part 3