Full Idea
Philosophical concepts of interest are rarely reductively defined; still more rarely does our understanding of such concepts rest on definitions. ...(We generally understand concepts to the extent that we know what role they play in thinking).
Gist of Idea
Philosophical concepts are rarely defined, and are not understood by means of definitions
Source
Theodore Sider (Writing the Book of the World [2011], 02.1)
Book Reference
Sider,Theodore: 'Writing the Book of the World' [OUP 2011], p.9
A Reaction
I'm not sure that I agree with this. I suspect that Sider has the notion of definition in mind that is influenced by lexicography. Aristotle's concept of definition I take to be lengthy and expansive, and that is very relevant to philosophy.