At the core of IIT is a single measure called “Φ” (the Greek letter phi, pronounced fy). The easiest way to think about Φ is that it measures how much a system is “more than the sum” of its parts, in terms of information. How can a system be more than the sum of its parts? A flock of birds provides a loose analogy: the flock seems to be more than the sum of the birds that make it up—it seems to have a “life of its own.”
In IIT, Φ measures the amount of information a system generates “as a whole,” over and above the amount of information generated by its parts independently. This underpins the main claim of the theory, which is that a system is conscious to the extent that its whole generates more information than its parts.
Seth, Anil. Being You (p. 64). Penguin Publishing Group. Kindle Edition.
Our usual way of thinking is cause and effect. In Western Civilization we tend to view and understand our experience of the world in a linear and reductive way. Seth’s idea of consciousness is a systems view, the whole is greater than the sum of its parts and it is this “greater than” that contributes to consciousness.
This idea of the whole being greater than the sum of its parts is a primary concept in family therapy where the dynamics of the family system, the roles and rules that govern its functioning, is the frame of reference and focus of perception and apprehension.
From this perspective one might ask “What kind of a family is this?” and “To what extent are they aware of how the system they participate in functions?” In other words, to what extent are members of the family conscious of its existence as a family unit and not just a collection of individuals?
A working definition of consciousness might be “the experience of experience.” The experience of experience is what Seth is naming “Phi.” Phi, claims Seth, is the measure of consciousness.