It is vain to do with more what can be done with less.

Never increase, beyond what is necessary, the number of entities required to explain anything.

Whenever two hypotheses cover the facts, use the simpler of the two.

Simpler explanations are, other things being equal, generally better than more complex ones.

When you have two competing theories that make exactly the same predictions, the simpler one is the better.

Pluralitas non est ponenda sine necessitate. A plurality (of reasons) should not be posited without necessity.

For nothing ought to be posited without a reason given, unless it is self-evident (literally, known through itself) or known by experience or proved by the authority of Sacred Scripture.