Full Idea
For Leibniz, to distinguish between a substance and its properties in order to provide a thing or entity in which properties can inhere leads necessarily to the absurd conclusion that the substance itself must be a truly characterless non-entity.
Gist of Idea
If a substance is just a thing that has properties, it seems to be a characterless non-entity
Source
report of Gottfried Leibniz (Monadology [1716]) by Cynthia Macdonald - Varieties of Things Ch.3
Book Reference
Macdonald,Cynthia: 'Varieties of Things' [Blackwell 2005], p.83
A Reaction
This is obviously one of the basic thoughts in any discussion of substances. It is why physicists ignore them, and Leibniz opted for a 'bundle' theory. But the alternative seems daft too - free-floating properties, hooked onto one another.