In an interesting passage from his influential work Phenomenology of Perception (originally published in 1945), philosopher Maurice Merleau-Ponty refers to the visual illusion where two equally long lines appear different. It is known as the Müller-Lyer illusion (see the picture below). Merleau-Ponty suggests that we are mistaken to think of these lines as equal or unequal because the comparison itself is impossible in this experiment. Why?
Our perception is always situated in an environment, it always proceeds in a context, against some sort of background that forms an essential part of what we perceive. Therefore, the experiment constructed in such an abstract, ‘laboratory’ style that strives to eliminate any ‘disturbing’ factors is actually too devoid of context to give us reliable insight into how our perception actually works. Those ‘disturbing’ factors are really important to our daily interaction with the environment.
Compare this with the Flying Man thought experiment devised by the 11th-century Islamic philosopher Avicenna.
“The two straight lines in the Müller-Lyer illusion are neither equal nor unequal, this is only an essential alternative in the objective world. The visual field is this strange milieu in which contradictory notions intertwine because the objects (the straight lines of the Müller-Lyer’s illusion) are not here placed in a domain of being where a comparison would be possible, but are rather each grasped in its own private context, as if they did not belong to the same universe.”
Maurice Merleau-Ponty
keep exploring!
P.S. Thank you for visiting me here on the humanfactor.blog! If you enjoyed this post and are interested in more philosophical content, I invite you to explore the blog, leave a comment, like, and subscribe to get notified of new posts.
Image credit: By Franz Carl Müller-Lyer, Franz Brentano – Brentano, Franz. ‘Über ein optisches Paradoxon’. Zeitschrift für Psychologie und Physiologie der Sinnesorgane, 3 (1892)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=109552640
humanfactor 