ABSTRACT. According to Livingston, Wittgenstein’s inquiry in Philosophical Investigations interrogates the deeply held assumptions that can make the structuralist picture of language seem obvious and unquestionable wherever the nature of language is in question. Kuusela emphasizes that Wittgenstein identifies the problem with metaphysics as an unclarity about the status of philosophical statements. Moyal-Sharrock notes that much of On Certainty fleshes out the distinction between certainty and knowledge.