Physiological Consequences of the Relativity of Perception Perception of the States of Matter: a Personal Reminiscence

The problem, as I perceived it, was how to introduce the abstract philosophical ideas of an eighteenth century philosopher into the scientific laboratories of the twentieth century. In particular, how did the anatomy and physiology of sensory perception reflect the Berkeleian notions of the relativity of existence? I did not query whether they did, only how they did. Somehow, the organism invests the world about it with the property of existence since, if there are no perceiving organisms, there is no world (using the second of Philonous’ states of existence and leaving God out of our equations). What constraints does this biocentric view place on the organs which mediate the process of perception? I was not successful in publishing my earliest thoughts on this subject (1965) until nearly two decades later. The first paper on relative perception that I succeeded in having published (in 1972) was a somewhat truncated form of my 1965 effort, and was entitled “The tactile discrimination of complex systems.” In this paper, the idea of “sensory receptor” is replaced by the idea of “sensory system,” for purposes of exploring how the states of matter are perceived. What anatomical-physiological system is required in order to perceive by tactile means the states of solidity, liquidity and elasticity? In order to perceive by tactile means whether an object is solid, it was argued, a human perceiver will prod the object with her / his fingertip, pressing the object at first gently and then more firmly. When the object is pressed gently, and found not to yield to digital pressure, can the perceiver conclude that the object is solid? It would depend on his or her personal definition of “solidity,” but generally, the answer would be no. A gel, for example, might not yield to very gentle digital pressure, but would not qualify for classification as a solid. If the substance being explored for solidity, such as my desk top as I write these words, does not yield under much firmer digital pressure, it will qualify as a solid. Now, as one presses firmly on the solid surface with her / his fingertip, there is compression of the tissues in the fingertip. Skin, subcutaneous tissue, and blood vessels are compressed until the solid object is placed in close apposition to the terminal phalanx (bone) of the finger. It would seem that we perceive solidity of state only when we invoke the solid tissue of the body. The tactile discrimination of the state of solidity is made only when the external object and the solid elements of the perceiving system are made contiguous. In brief, we need a solid to perceive a solid. Or, turning the matter around to express it from a biocentric point of view, we invest the world with the property of solidness only by possessing the anatomical property of solidness. By extrapolation, we might state that one can never perceive a degree of hardness in excess of the hardness of bone in the finger (cf Mohs’ scale of hardness). It might also be argued that organisms without solid elements in their bodies cannot be capable of perceiving, by tactile means, the state of solidity. Similar considerations can be extended to the tactile perception of the state of liquidity. Consider the experiment of Meissner (cited by Ruch and Fulton, 1960, p. 314), where the finger is immersed into a vessel of mercury. Meissner showed that the sense of pressure does not issue from the submerged portions of the finger, but only at the interface between air and mercury. Now, where the finger is immersed in the liquid mercury, the immersed portion is compressed and, presumably, the volume of the immersed part is reduced. The reduction in volume will occur because blood and possibly