Perceptual illusions are extremely interesting and complex phenomena that, far from being mere surprising visual attractions, are very useful tools both for cognitive scientists and philosophers of mind. In a scientific context, illusions reveal the failures of perception and the disfunctions of our sensory apparatuses, indicating the limits of human’s perceptual system. Moreover, these phenomena allow to analyze the cognitive sub-processes underlying perception. In the philosophical sphere, illusions bring to light various problems within philosophical theories of mind and perception.
In this paper, I present the complex perceptual content of some static configurations that elicit the impression of movement: Waterfall Illusion, Peripheral Drift Illusion, Pinna Illusion and some Op Art. Besides showing the causes of the detachment between physical stimulus and phenomenology, I reflect on two distinct, but inevitably intertwined, aspects of their content. On the one hand, I stress the importance of that phenomenological component called “illusoriness” – a phenomenal attribute related to a sense of strangeness, deception, singularity, mendacity, and oddity (Pinna et al. 2018). On the other hand, I ask if it is really true that the illusory experience of these phenomena implies an impossible or paradoxical perceptual content. According to various psychologists and philosophers, since at the same time I see the same object move and remain still, these experiences would manifest a logical contradiction.
Lastly, intertwining the analysis of the illusoriness and the paradox with the empirical data provided by the sciences of the mind, I try to show that, in the cases examined, there is no manifestly contradictory content. Moreover, as the majority of the illusions considered are images, I draw some conclusion concerning the depiction of motion in static images.