The present essay introduces and discusses two important aspects of Wittgenstein’s philosophy. The first one is his insistence on the fact that philosophical investigations are conceptual or grammatical investigations, not to be confused with factual investigations. It will be shown that it is exactly this kind of confusion between the conceptual and the factual, which characterizes, according to Wittgenstein, metaphysical thinking. The second aspect, narrowly connected to the first one, concerns the way in which Wittgenstein tries to show that conceptual or grammatical investigations must take into account the correspondence obtained between our grammar or our conceptual formations on one hand and many general facts of nature on the other, without therefore becoming or taking up the form of a natural science or natural history.
Keywords: Concepts, Grammar, Metaphysics, Nature, Psychology, Wittgenstein