A short selection from Essay Thirty-one in Darwin, Dogen, and the Extremophile Choice. [YOU MIGHT WANT TO SKIP THIS ON A FIRST READING OF THE TWO BUDDHAS SEQUENCE]
It may very well be that in our conscious inner lives the interplay among the senses is what constitutes the sense of touch. Perhaps touch is not just skin contact with things, but the very life of things in the mind? —McLuhan 
That even Marshall McLuhan, author of Understanding Media (1964), saw touch as the product of sensory interplay, rather than as the sensory framework, or primary means, by which we think, is evidence of the deep resistance our thinking minds have to admitting the co-dependent and transitory nature of the ‘self’. Even though it was suggested many years ago (e.g. Wilder Penfield and Oliver Sacks—writing after McLuhan) that a physiological ‘sense of self’ is generated by various kinaesthetic organs that tell us how our joints, tendons, and voluntary muscles are moving (a wide array of other proprioceptors generates internal sensation elsewhere in the body); and while it’s also obvious that only our skeletal muscles can reshape, and conform to the rest of the world, the quite separate light touch system at the body’s intervening surface (the skin has different receptors for soft-contact, pain, heat, and cold); yet our thinking minds remain concertedly blind to the role of this deep sixth sense when we construct our phenomenologies. One reason is surely that deep touch is the only sense that’s accompanied by efferent impulses—i.e. movement is voluntary. In fact, efferent and afferent are so indistinguishable here that I will continue to use the one word, kinaesthesia, to mean both.
Speaking from experience, I am convinced that the best carpenters make practical ‘sense’ of the messages coming from their eyes—as they scan a drawing or a built framework for instance—only because they use their bodies to under-stand connectivity itself. And yet my reading on the subject reveals only this: that ever since literary men first began to write down their philosophies, the objects of perception have typically been de-scribed in primarily visual terms. One might be excused for wondering if this is a practised (but not necessarily deliberate) oversight, due to the need of indelible author-ity to verbally and pictorially grasp at the hope of a non-material, and non-mortal, self-possessed mind. Or perhaps it’s just that the semiotician’s background-foreground illusion has not yet been seriously considered at this deepest of all cognitive levels. The illusion in fact must be absolute for sensible human beings who naturally hesitate to take that absurd final step of ‘thinking’ medium vs message where these are so finally thus.
When you take into account the full subtlety of behaviour (see my attempt at an anatomy in the next essay, 32), then abstract forms like Kant’s pure intuition (Anschauung),  and Descartes’ soul, or mental substance, become sensible as the body’s covert (thus ‘abstracted’) activity. Descartes’ anatomy of the sensorium followed that of Galileo, who made a distinction between the secondary qualities, which arise from the five bodily senses of sight, sound, smell, taste and light touch, and the primary qualities that belong to the ‘objects’ of sense. The empiricist Locke, who deemed the primary qualities, “bulk, figure, number, situation, and motion or rest”, to be sensible as touch —even citing the “experience of resistance”—still explicitly disembodied his “inner sense” of “mental operations”; this implies he did not recognize kinaesthesia as the kind of sense that would make these qualities ‘secondary’. But if we accept that these ‘solid’ truths, and our thoughts about them, are derived from motor-sense, this would necessarily make them secondary fabrications; so why insist on making this distinction in the first place? Is this expedient the author-ized beginning of the mind-body dualism illusion? In the Age of ‘objective’ (and visual) Enlightenment?
That even optical illusions, hard-wired in the eyes and brain, must be registered (in some cases explained) by a body with its own logistical limitations, just means our inner lives are more tangible than the thinking mind wants to admit.  And in fact we do find phenomenologies that get around the dualistic five senses plus a soul fixation: all the while Western philosophers had their suspicions (and talked around them), and long before modern physiology located all the bodily senses, farther to the East, in meditative stillness and silence, the mind itself was easily recognized as the body’s “sixth sense”.
1. McLuhan, Marshall. 1964 Mentor paperback second edition. Understanding Media: The Extensions of Man New York: McGraw-Hill, p. 105.
2. Kant, Immanuel. 1970 Mentor Books edition, “Critique of Pure Reason” , F. Max Muller, trans., in Arnulf Zweig, ed. The Essential Kant. New York: The New American Library. pp. 42-294. From p. 60: “Now it is clear that it cannot be sensation again through which sensations are arranged and placed in certain forms. The matter only of all phenomena is given as a posteriori; but there form must be ready for them in the mind (Gemüth) a priori, and must therefore be capable of being considered as separate from all sensations.” Here, once again, covert behaviour is not detected as ‘sensible’.
3. Locke, John. 1974 Anchor Books edition, “An Essay Concerning Human Understanding”  in Prof. Richard Tayler abridge. The Empirisists. Garden City NY: Doubleday. pp. 7-133. These quotes from: pp. 9-30.
4. At the time of this post we are finally beginning to understand the role of kinesthesia in cognition in terms of neuroscience. See Buzsaki, Gyorgy. June. 2022. Constructing the World from Inside Out. Scientific American, vol. 326, no. 6, pp. 37-43: “Perception then can be defined as what we do — not what we passively take in through our senses.” p.40. and “In this sense, our thoughts and plans are deferred actions, and disengaged brain activity is an active, essential brain operation.” p. 43.