In the time of William Shakespeare, there were commonly reckoned to be five wits and five senses. The five wits were sometimes taken to be synonymous with the five senses, but were otherwise also known and regarded as the five inward wits, distinguishing them from the five senses, which were the five outward wits.
Much of this conflation has resulted from changes in meaning. In Early Modern English, "wit" and "sense" overlapped in meaning. Both could mean a faculty of perception (although this sense dropped from the word "wit" during the 17th century). Thus "five wits" and "five senses" could describe both groups of wits/senses, the inward and the outward, although the common distinction, where it was made, was "five wits" for the inward and "five senses" for the outward.
The inward and outward wits are a product of many centuries of philosophical and psychological thought, over which the concepts gradually developed, that have their origins in the works of Aristotle (who only defined four senses, however). The concept of five outward wits came to medieval thinking from Classical philosophy, and found its most major expression in Christian devotional literature of the Middle Ages. The concept of five inward wits similarly came from Classical views on psychology.
Modern thinking is that there are more than five (outward) senses, and the idea that there are five (albeit that it superficially matches the gross anatomical features — eyes, ears, nose, skin, and mouth — of many higher animals) does not stand up to scientific scrutiny. (For more on this, see Definition of sense.) But the idea of five senses/wits from Aristotelian, medieval, and 16th century thought still lingers so strongly in modern thinking that a sense beyond the natural ones is still called a "sixth sense".
These are the v. wyttes remeuing inwardly:
Fyrst, commyn wytte, and than ymaginacyon,
Fantasy, and estymacyon truely,
And memory, as I make narracyon;
Each upon other hath occupacyon.
Stephen Hawes, The Pastime Of Pleasure, XXIV "Of the Five Internall Wittes"
Hering, sight, smelling and fele,
cheuing er wittes five,
All sal be tint er sal pas,
quen þe hert sal riue.
Cursor Mundi, lines 17017–17020
Sounds interesting... I wonder what to do with it :-D
"Chewing, the fifth sense..."