But the same is true of the other senses.
[ul]
[li]It’s one thing to realize your hand is in a pot of scalding water. It’s another thing to pull it out.[/li][li]It’s one thing to realize the milk you just sipped is sour. It’s another thing to spit it out.[/li][li]It’s one thing to realize someone just shined a bright light in your eyes. It’s another thing to shade or close them.[/li][li]It’s one thing to realize Ashlee Simpson is playing on the radio. It’s another thing to change the station.[/li][li]It’s one thing to beat a dead horse with a fifth example. It’s another to plug your nose so you don’t smell the rotting corpse.[/ul] [/li]
This is a bit of a circular argument. You’re basically saying that because balance isn’t a sense, you can’t sense balance. But you haven’t given an argument for why balance isn’t a sense.
The ability to detect a gravational (or acceleration) field sounds like a sense. Hearing is the ability to detect sound waves, sight visable lightwaves, touch is the ability to detect the electroweak force (or is it the strong one). All these things tell you about something outside your body.
Yes it’s not the most popular sense in the body but that’s no reason not to respect it.
The traditional “five senses,” as formulated by Aristotle, are a highly arbitrary categorization of the senses we actually have. As others have pointed out, we have several senses in addition to the traditional five, and the so-called sense of touch consists of at least five distinct senses. Personally, I would put the number of separate senses we have as at least 12, and probably more.
Sight: detection of light in the visible spectrum
Hearing: detection of sound waves in air
Smell: detection of airborne chemical particles
Taste: detection of chemical particles in contact with the tongue and mouth.
“Touch”: these various senses have traditionally been grouped because the receptors are mostly in the skin, but the receptors are quite distinct:
Heat
Cold
“Touch” (light pressure)
“Pressure” (deep pressure)
Pain
Actually, it is even more complex than that; there are a variety of subgroups among these receptors, and it would be possible to subdivide the sense of “touch” even further.
“Balance”: The so-called “sense of balance” itself consists of at least two different senses, mediated by different parts of the vestibular organ in the ear:
Gravity/linear acceleration. Gravity and linear acceleration are both sensed by the otolith organs within the vestibular organ
Rotational acceleration. Rotation in three dimensions is sensed by the three semicircular canals
Finally,
Proprioception: The sense of where the parts of the body are, detected by receptors within the muscles and tendons.
The senses of “touch,” “balance,” and proprioception are sometimes distinguished as a groups as the “somatic senses,” in distinction to the “special senses” of sight, hearing, smell, and taste.
Still additional senses could be recognized, such as the senses related to the internal organs - stomach fullness, stomach ache, visceral pain - which are distinct from the senses of “touch.”
Exactly how the various senses should be categorized is debatable, but saying that there are just five of them is clearly an over simplification.