If you’re not blind, and you’re not in total darkness, as soon as you open your eyes you see colors. Red, blue, yellow, green… There are way too many colors for the few words we have.

Where do these colors come from? Are the colors in the physical particles of the universe or do our retinas and brains “give color” to the world? Or are all these colors “born” from the meeting between the particles of the world, their wavelengths, and the cellular networks of our brains? What does a “wavelength” mean, and how does such a physico-mathematical characteristic appear as a shade of color?

Here are what I consider to be the most important and fundamental questions in the fields of biology, psychology, neuroscience, physics, philosophy…

The question of the “appearance” of colors is only a simple example that I took to introduce the gigantic phenomenon or problem of qualia.

The problem and the solution of the qualia is probably the greatest scientific mystery to be solved in all branches of science. Consider for example the following questions.

Where do smells come from? How do flowers produce their odors? Where exactly are they found? To answer these questions, do you need to go to a physicist, or a specialist in the anatomy of the nose, or both?

Where does the taste of an apple come from? Of an orange? A sardine or a tomato? In the molecules of these things? Or in the way the cells of the tongue are connected with the cerebral cortex?

Where does the flow of time come from? Does time really flow? Or is it just an impression we have created by observing movements? To answer these questions, should we go see a clockmaker? A physicist? A psychologist? A specialist in the anatomy of neurons?

Where do ugliness and beauty come from? Good and evil? Justice and injustice? Heaven and hell? Harmony and chaos? Heat and cold? Where do history, memory, movement, music come from?

Where does the fact that mathematical formulas can accurately predict the area of a circle come from? Where is the number pi? In the world, or in the neurons? Or in both?

Fundamentally, what is the relationship between physics (molecular, atomic, quantum, mathematical) and biological nature (organs, cells, proteins, amino acids, DNA, evolution)?

* In philosophy of mind, qualia (/ˈkwɑːliə/ or /ˈkweɪliə/; singular form: quale) are defined as individual instances of subjective, conscious experience. The term qualia derives from the Latin neuter plural form (qualia) of the Latin adjective quālis (Latin pronunciation: [ˈkʷaːlɪs]) meaning “of what sort” or “of what kind” in a specific instance, such as “what it is like to taste a specific apple — this particular apple now” (from Wikipedia).