This book offers two claims about Wittgenstein's views on perception as explored in the Philosophical Investigations. The first is an interpretive claim about Wittgenstein: that his views on sensation and perception, including his critique of private language, have their roots in his reflections on sense-datum theories and on what Hymers calls the misleading metaphor of phenomenal space. The second claim is that Witgenstein's critique of the misleading metaphor of phenomenal space is of ongoing relevance to current debates concerning first-person authority and the problem of perception because we are still tempted to draw inferences about the phenomenal that only apply to the physical.