 Aristotle also considers higher-order perception and thought. He offers a regress argument at the beginning of On the Soul III 2 to show that when we perceive that we see or hear, we have a higher-order perceptual awareness of the first-order perceiving (425b12–25) and, while the precise details are a matter of controversy, it is arguably the same act of perception being directed at itself (Caston 2002b; for a response, see Johansen 2005). But Aristotle elsewhere claims that in general states like knowledge, perception, belief, or thought are always directed at something else primarily and themselves only peripherally or “on the side” (en parergōi); only God’s self-reflexive thinking, which he characterizes as a “thinking of thinking” (noēsis noēseōs), has itself as its primary object (Metaph. XII 9, 1074b34–36). Self-directed intentionality raises a number of questions, in particular whether Aristotle is committed to it being a part of every mental act – as he seems to claim at Nicomachean Ethics IX 9, 1170a29–b1, which Brentano 1874 [1995], Book II, chs 2–4 takes up and champions – and whether he thinks it is possible to be in error about the content or character of the first-order state, even if not about its existence (Caston 2002b).