Knowledge of the physiology and anatomy of the human body should tell us a lot about how our sense data is processed in the brain. Yet, relatively little is known about how the brain processes these sensations, or what it is like to perceive them. Consciousness is notoriously hard to define, and explanations tend to be in philosophical, subjective terms. In 1892, William James coined the term stream of consciousness to describe the continuous process by which thoughts and perceptions occur.
We know what it means to be conscious, but do we really know what we are conscious of? How do we recognize and measure awareness in others? They obviously can tell us about their experiences, but these are just as subjective as our own. Medical criteria for consciousness may be based on response to sensory stimuli, but they offer no insight into a person’s self-awareness. An examination into brain activity during various states of consciousness does reveal something of a person’s awareness, but it tells us little of their subjective experience.
