 Tsongkhapa characterizes basic ignorance (Sk. avidyā), the root cause of suffering in Buddhist philosophy, not as a latent tendency, but as an active defiling agency (Sk. kleśāvaraṇa) that projects a reality onto objects that is in fact absent from them. This ignorance affects even sense perception and explains the veridical aspect that is, in fact, just error. The residual impressions left by distortion (literally “perfumings” Sk. vāsanā) explain the mere appearance of things as real. Beyond that, he asserts that habituation to this distortion prevents conventional and ultimate reality from appearing united in an appearing object. This explanation of the psychology of error differs markedly from earlier Tibetan explanations and constitutes the sixth difficult point.