Two bodies are said to be touching if there is no spatial gap between some point on the surface of one and some point on the surface of the other. If one of the touching bodies is that of a sentient being, it may be aware of certain properties of the other body: for instance, that it is hot or cold, rough or smooth, wet or dry, hard or soft, sweet or sour. The sentient being is said to be aware of an object's sweetness or sourness by taste. (Aristotle attributes our distinguishing taste from touch to the fact that only a part of our flesh is sensitive to flavor.) The remaining properties the sentient being is said, in common speech, to be aware of by touch. Accordingly, touch appears in the traditional list of senses, with sight, hearing, and so on.

Aristotle

Aristotle remarks that in the...