In this paper, I discuss aspects of Herbert Leyendecker’s 1913 doctoral dissertation, Towards the Phenomenology of Deceptions, which he defended in 1913 at the University of Munich. Leyendecker was a member of the Munich and Göttingen Phenomenological Circles. In my discussion of his largely neglected views, I explore the connection between his ideas concerning “attitudes”, e.g., of searching for, observing, counting, or working with objects, and the central topic of his text, perceptual illusions, thematized by Leyendecker as a kind of (...) perceptual “deception”. Indeed, Leyendecker argues that a change of attitude is a necessary aspect of an illusion. I argue that Leyendecker’s use of the notion of attitude in accounting for illusions is problematic; yet I also suggest that his ideas are not devoid of philosophical interest, in relation to current debates. (shrink)