When we speak of consciousness at the level of the brain as a whole, we are implicitly taking a materialist philosophical perspective. In other words, we are embracing the idea that it is the brain—and hence, physical matter—that engenders the human mind. We are also accepting that the activity of the brain’s neurons is the source of all our mental processes, such as learning, memory, perception, and language, and hence of consciousness, which in a sense emerges from all of the brain’s other attributes and so is no exception to this rule.

Once we start talking about the brain and consciousness, we must necessarily begin talking about the unconscious as well, because the brain has many specialized circuits that are constantly decoding various aspects of our environment without our being conscious of their doing so. Likewise, the vast majority of our behaviours occur automatically, without our being conscious of having initiated them. The same goes for our mother tongue, whose grammar we use correctly without even realizing it. One last example: some people suffering from brain damage can perform certain tasks correctly without being conscious of doing so.

Ultimately, we cannot deny that the vast majority of everyone’s life is governed by unconscious circuits in the brain. Even so, the stream of consciousness remains a constant presence in our daily lives. And as we are about to see, our conscious states involve extensive areas of our brains