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

Entities are not to be multiplied beyond necessity.

Entities should not be posited unnecessarily.

Entities must not be multiplied beyond necessity.

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

3 is a prime, 5 is a prime, and 7 is a prime. Why bother with non-prime numbers when the primes can do everything?

Entia non sunt multiplicanda praeter necessitatem