Full Idea
The medieval philosophers and then Leibniz were keen on finding 'principles of individuation', and the idea appears again in Frege, to be taken up in some respects by Wittgenstein.
Gist of Idea
Individuation was a problem for medievals, then Leibniz, then Frege, then Wittgenstein (somewhat)
Source
C. Anthony Anderson (Identity and Existence in Logic [2014], 1.6)
Book Reference
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.60
A Reaction
I take a rather empirical approach to this supposed problem, and suggest we break 'individuation' down into its component parts, and then just drop the word. Discussions of principles of individuations strike me as muddled. Wiggins and Lowe today.