«Next, we say that the principles we seek are such that we may demonstrate that from them the stars, the earth, etc., could have arisen. [ ] Now to discover these causes, the following are the requirements of a good hypothesis.

1. Considered only in itself, it must not imply any contradiction.
2. It must be the simplest that can be.
3. Following from (2), it must be very easy to know.
4. Everything that is observed in the whole of nature must be able to be deduced from it.»


Spinoza, Principles of Cartesian Philosophy, Part 3