Maurice Merleau-Ponty: The World of Perception - Timothy R. Quigley

In the footsteps of science and painting, philosophy and,above all, psychology seem to have woken up to the fact thatour relationship to space is not that of a pure disembodiedsubject to a distant object but rather that of a being whichdwells in space relating to its natural habitat. This helps us tounderstand the famous optical illusion noted by Malebranche:when the moon is still on the horizon, it appears to be muchlarger than at its zenith. 5 Malebranche assumed that humanperception, by some process of reasoning, overestimates thesize of the planet. If we look at it through a cardboard tube orthe cover of a matchbox, the illusion disappears; so it is causedby the fact that, when the moon first appears, we glimpse itabove the fields, walls and trees. This vast array of interveningobjects makes us aware of being at so great a distance, fromwhich we conclude that, in order to look as big as it does,notwithstanding this distance, the moon must indeed be verylarge. On this account, the perceiving subject is akin to the scientistwho deliberates, assesses and concludes and the size weperceive is in fact the size we judge. This is not how most oftoday’s psychologists understand the illusion of the moon onthe horizon. Systematic experimentation has allowed them todiscover that it is generally true of our field of vision that theapparent size of objects on the horizontal plane is remarkablyconstant, whereas they very quickly get smaller on the vertical55