What was Wittgenstein's attitude to science and how did it affect his conception of psychology and philosophy? Wittgenstein's remarks about science have struck many of his readers as anti-science and hence irrational. This "anti-science" reading has affected the reception of his remarks on philosophical psychology. The received view is that Wittgenstein makes the wrong-headed, even pernicious, claim that philosophical psychology can and should proceed without due attention to the psychological sciences. One aim of this paper is to show that what others have understood as anti-science, is really anti-scientism. Another is to show that Wittgenstein's concern about scientism is one instance of a more general concern about self-deception, and that this concern is a single, main trackable thread that runs through his work. Moreover, we aim to show that Wittgenstein's reservations regarding overly-scientific psychology and philosophy help illuminate what has become a classic problem in modern philosophical psychology: the nature of self-deception itself. Altogether we aim to show that his concerns with self-deception were intended to discipline our thinking, in all its forms.