I would like some suggestions about Concept Formation. Especially if there is a reference to Plato's Theory of Forms. I believe the two are linked but cannot find appropriate material. Thank you.
You can consider the "classical" theory of concept, from Plato to Frege.
See "On Concept and Object" (originally published as "Ueber Begriff und Gegenstand" (1892)) : the application of a concept can be completely specified by discovering a set of necessary and sufficient conditions that define the objects falling under the concept. These conditions constitute the analysis of the concept (according to grammar : its definition).
And you can compare it with Ludwig Wittgenstein's account, exposed into his Philosophical Investigations (published posthumously, in 1953), of family resemblance of concepts.
See also Language game.
And see Joachim Schulte, Concept Formation, into Nuno Venturinha (editor), Wittgenstein after his Nachlass, Palgrave (2010), page 128-on.