Full Idea
Occam's Razor should only be understood to concern substances: do not multiply basic entities without necessity. There is no problem with the multiplication of derivative entities - they are an 'ontological free lunch'.
Gist of Idea
We should not multiply basic entities, but we can have as many derivative entities as we like
Source
Jonathan Schaffer (On What Grounds What [2009], 2.1)
Book Reference
'Metametaphysics', ed/tr. Chalmers/Manley/Wasserman [OUP 2009], p.361
A Reaction
The phrase 'ontological free lunch' comes from Armstrong. This is probably what Occam meant. A few extra specks of dust, or even a few more numbers (thank you, Cantor!) don't seem to challenge the principle.