Different Forms of Sense Perception does not Invalidate Sense Perception

The senses don’t distort, and this is not invalidated by the fact that different creatures have different forms of sense perception. A color-blind man is able to deduce the same laws of physics as one with a greater ability to distinguish between hues (note that no human is able to distinguish between radio- and infrared-rays of light using his eyes, and yet we know of their existence)—assuming no errors are made. Even a totally blind man could deduce that other men are capable of seeing by various tests, he could validate that they are able to figure out what objects are without coming into physical contact—the same is true for Martians, who share no senses with us, they would still be able to deduce the same laws of physics. A caveat to this is that different forms of sense perception lead to different capabilities in deducing laws.

Ayn Rand observes […] that a difference in sensory form among perceivers is precisely that: it is a difference in the form of perceiving the same objects, the same one reality. Such a difference does not pertain to cognitive content and does not indicate any disagreement among the parties. The senses of a man with normal vision, to take the standard example, do not contradict those of a color-blind man. When the former says about some object, “It is red,” he must in reason mean by the statement: “It is an entity in reality of a specific nature such that, when it acts on my senses, I perceive it in the form of red color.” That is true; that is what it is. Similarly, if the color-blind man says “It is gray,” he has to mean: “It is an entity in reality of a specific nature such that, when it acts on my senses, I perceive it in the form of gray color.” That also is true; that is what it is. Neither statement conflicts with the other. Both men are perceiving that which is and are doing so in a specific form.

Nor will these two men or any other perceiver with an intellect come to different conclusions about the nature of the object. In this respect, differences in sensory form do not matter. They have no consequences in regard to the content of cognition.¹