 Al-Haytham held that many perceptions are inferential, and he explains his views in II.3 of the Optics. Rather than always grasping sensed things in an unmediated way, he argues, we sometimes grasp them through sudden, “imperceptible” inferences. These inferences proceed so rapidly as to seem immediate, and thus we usually don’t notice that they are occurring at all. Al-Haytham even argues that seemingly self-evident propositions such as “the whole is greater than its [proper] part” are inferential. Given this inferential process, cognitive error becomes a more reasonable possibility.