Christof Koch writes:

What is common between the delectable taste of a favorite food, the sharp sting of an infected tooth, the fullness after a heavy meal, the slow passage of time while waiting, the willing of a deliberate act, and the mixture of vitality, tinged with anxiety, just before a competitive event?

All are distinct experiences. What cuts across each is that all are subjective states, and all are consciously felt. Accounting for the nature of consciousness appears elusive, with many claiming that it cannot be defined at all, yet defining it is actually straightforward. Here goes: Consciousness is experience.

That’s it. Consciousness is any experience, from the most mundane to the most exalted. Some distinguish awareness from consciousness; I don’t find this distinction helpful and so I use these two words interchangeably. I also do not distinguish between feeling and experience, although in everyday use feeling is usually reserved for strong emotions, such as feeling angry or in love. As I use it, any feeling is an experience. Collectively taken, then, consciousness is lived reality. It is the feeling of life itself.

But who else, besides myself, has experiences? Because you are so similar to me, I abduce that you do. The same logic applies to other people. Apart from the occasional solitary solipsist this is uncontroversial. But how widespread is consciousness in the cosmos at large? How far consciousness extends its dominion within the tree of life becomes more difficult to abduce as species become more alien to us.

One line of argument takes the principles of integrated information theory (IIT) to their logical conclusion. Some level of experience can be found in all organisms, it says, including perhaps in Paramecium and other single-cell life forms. Indeed, according to IIT, which aims to precisely define both the quality and the quantity of any one conscious experience, experience may not even be restricted to biological entities but might extend to non-evolved physical systems previously assumed to be mindless — a pleasing and parsimonious conclusion about the makeup of the universe. [Continue reading…]