"Touch" most frequently refers to the sense of touch, defined by the Oxford English Dictionary as "That sense by which a material object is perceived by means of the contact with it of some part of the body."1 It is associated with the hand, and the art of sculpture.
Compared to the other senses, touch is both immediate and unmediated. There is no time-delay beyond nerve impulse, and no medium through which the stimulus travels between the subject and the object. Sight, hearing, smell, and taste depend emanations (i.e., chemicals, vibration, reflected light) that travel through an "intervening substance" such as air or water.2 Touch, on the other hand, places the sensing organ in direct contact with the sensed object.
Beyond this lack of mediation, touch is distinguished by its position as the basic sense. Taste, certainly, is dependent on touch - not merely for the necessary physical contact, but also because of the role that texture plays in tasting. Hearing shares with touch both many aspects of the physiological process and much of the same language. Sound and music are described most frequently in synaesthetic (2) terms, applying language of touch and texture - hard, soft, sharp, round, warm, smooth - to different tones and arrangements.
As for vision, Descartes suggested that it was based in the tactile sense, essentially an extension of touch that, like a blind man's cane, probes the shapes and textures of his surroundings.3 Though his proposal is not truly scientific, it has indeed been observed that the blind, when they gain sight through surgery, can transfer tactile knowledge into visual knowledge. In one particular case, the newly-sighted individual could not identify a lathe, nor see any part of it beyond the suggestion of a handle, until he was allowed to touch it and feel its parts, at which point he commented, "Now that I've felt it I can see."4 These are admittedly exceptional cases, but the fact that such a sensory relationship can occur does indicate that the blind man is not forming an "image" of the area analogous to vision; instead, his visual world is bounded by his tactile experience.
Another distinction of the sense of touch is that it is identified with the real. You can't believe your eyes, nor your ears, and taste is personal and subjective, but touch is proof. When Thomas doubts the resurrection of Jesus in the book of John, the confirmation he demands is that of the sense of touch: "Unless I see the mark of the nails in his hands, and put my finger in the mark of the nails and my hand in his side, I will not believe."5 Touch is not imagistic but physical, direct contact that we suppose cannot be fooled.
Touch is also, when between two subjects capable of touch, by necessity reciprocal and essentially unmediated. The medium of the touch would be the hand or other body part, but in this case the medium is also the receptor, and the touch puts two receptors into direct contact.
To understand the literal sense further, we must look at its negation, namely, the forbidding of touch. We're all familiar with the basic concept - "Look but don't touch," "Keep your hands to yourself," and so forth. Touch is transgressive. We have our personal space, we have our private parts. Entire classes of people, animals, or objects may be labeled "untouchable," out of reverence, fear, or contempt. In the New Testament book of Colossians, Paul questions the ancient rules, "Do not handle, do not taste, do not touch."6 These certainly are universal concerns. In his paper on iconoclasm, Bruno Latour quotes extensively from a story by Bharathipura, describing an individual's attempts to violate both a holy relic and the class structure by forcing the Untouchables to touch it.7 Old Testament law precisely defines which people and which foods cannot be touched, and when. In America, physical contact between those who are not intimate is limited by specific customs of greeting and cultural.
This transgressive power lies in the intimate nature of touch. The only sense more intimate than touch is taste, which both requires touch and is unlikely to emerge as a problem in normal circumstances. Of the rest, only sight is directed enough to have social ramifications because of its intimacy (the nudity taboo, for example), but it is still far less transgressive - you can look, but not touch. Touch is physical, and, as previously mentioned, reciprocal and unmediated. It has, as a result of this intimacy, picked up erotic connotations: "To have sexual contact with" and "to masturbate," as the OED defines it.8
A final use of the literal touch is the mystical and healing touch. Blessings are transferred by touch, touch confers knighthood, laying on of hands heals the body, and the touch of the king was thought in England to cure scrofula.9
The most important nonliteral meaning of touch is as a metaphor for communication, seen in such phrases as "get in touch," "make contact with," and "reach out and touch someone." "It begins to be evident that "touch" is not skin but the interplay of the senses," McLuhan wrote, describing the metaphors as representing "a fruitful meeting of the senses."10 Our channels of communication are created and maintained through a metaphor of physical contact. Touch is, also, direct contact, without medium or distance. By "getting in touch," the barriers of distance fall away.
Literal touch can be used to communicate, as Helen Keller well knew, but the touch described in the metaphor is more. It maintains the reciprocal nature of a physical touch, and implies a mental/social contact as direct as the hand.
Touch also can be used to describe emotional relations. When we see something particularly beautiful, or find our compassion aroused, we have been "touched" - something about the touching subject has made contact with us, emotionally. This ties back to intimacy, as well. Only that which is truly important to us can be described as "touching" us, and to apply the term to unimportant people and art would approach self-parody.
This emotional link becomes even clearer when we notice that all of our emotions are discussed in terms of touch. When we are touched by the plight of another, we feel sympathy.11 We feel angry or sad or happy as though the emotions were external objects - Platonic forms, perhaps - that we are put into contact with. This same construction is used, as well, to describe physical states ("I feel sick") and the actual characteristics of an object that the sense of touch can give us information about ("The table feels rough/polished/warm").
A final figurative sense of touch is the concept of influence, a mode very similar to that of emotional description. McLuhan claimed that America, at the time of his writing, was "profoundly "in touch" again with European traditions of food and life and art."12 America was moving with Europe, influenced by its ideals. We are "in touch" when we know the trends and happenings in society, "touched" when we've lost our minds, or "touched by the gods" if we happen to be truly blessed.13 And who hasn't heard a devout Christian talk about how Jesus touched them? Such cases are very similar to emotional touch, in that the description implies contact with Something Else, which alters the individual. Literal political and social influence can use the same sort language. "The long arm of the law might be difficult for petty criminals to escape," one might say, "but money and power can make one seemingly untouchable."
One of the most significant extensions of touch is the weapon; touch, after all, can mean a "strike" or "blow."14 Something like a club is obviously a literal extension of the fist, and McLuhan describes the rifle as "an extension of the eye and the teeth."15 The weapon lets the wielder strike his foe with more force and distance than the fist.
It seems, however, that at a certain point the relationship between the touch and the weapon disappears. Describing something like a missile as an extension of the hand feels strange, as the missile lacks the characteristics associated with touching another. There is no direct connection when the foe is nothing more than in the blast radius, and the actions of the individual firing the missile seem far divorced from the origins of combat.
Another example of media extending touch would be remote surgery, in which a surgeon can, using remote controllers and robotic analogues, operate on a patient across the world.16 In some systems the reciprocal touch can be replicated, with tactile feedback and resistance giving the surgeon actual tactile sensory input.
The figurative aspects of touch can also be seen as extended. Sympathy, for example, is defined as "The quality or state of being affected by the condition of another with a feeling similar or corresponding to that of the other."17 We extend our senses, through sympathy, to feel the emotions of another.
The metaphor of touch might also make one look on communication technologies as extensions of touch. A telephone, for example, can be seen as extending the voice and the ear, but it is just as useful to look at it as extending one's physical presence. The connection of physically getting-in-touch is extended over distances through the medium of the telephone.