Every area of knowledge begins in the question: What is reality? If I see an apple, is it real? If I see some work of art and think it is beautiful, is it really beautiful? Is money real? Is power real? Is objectivity real? Does she really love me? The question of reality pervades every aspect of our existence, and it is no surprise that it appears within science and philosophy as well.
How we perceive taste, smell, touch, sound and sight is a fact about our perception, but it has never been properly understood in biology, psychology, or philosophy. The problem is that we suppose material objects to be length, mass, charge, momentum, energy, temperature, etc. How these physical properties become taste, touch, smell, sound, and sight remains a mystery because the sensations have qualitative properties (and are described as types) while the objects do not. If eyes, nose, ears, skin and tongue are material objects, then they could only have physical properties, not qualities. How can then we perceive qualities?