Touch is the earliest of the human senses to develop. It is already functioning during the seventh week of pregnancy, long before the ears or the eyes are fully formed. And it is literally the broadest of the senses, since the skin, where the touch receptors are found, covers the entire body.
At birth, babies use their sense of touch in their first efforts to understand their surroundings. Even after they have learned to recognize things by sight, they often try to confirm what they see through touch - by patting their mothers' faces or reaching out to the sides of their cribs.
Adults also seem to regard touch as fundamental. How often do you find yourself not believing what you see until you have actually felt it? A sign saying "Wet Paint," for example, often serves less as a warning than as an invitation to touch the paint and find out how wet it really is.