Plurality should not be assumed without necessity.

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

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

Plurality is not to be posited without necessity.

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

No more things should be presumed to exist than are absolutely necessary.

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?