This is the process where one observes their own self in a purely subjective manor. This is done by observing the inner workings of one’s own brain. If someone has never engaged in introspection, it is likely that there are processes that regularly occur within this person’s brain that they can become consciously aware of through introspection. Conscious awareness is a purely physical feature of the brain and is not related to the concept of phenomenal consciousness. The human brain has a feature that allows it to focus its attention to a small number of subjects (often only one) at any given time and from this these subjects can be analyzed and better understood. This does not imply that there is a specific part of the brain that acts as the “command center” and through which conscious awareness is possible. This is a purely functional feature of the brain that is implemented by certain types of organized communication among brain cells.

The information that can be gained from introspection is severely limited because it is only possible to observe a very small portion of the processes that occur at any given moment inside the brain. Most brain processes are subconscious, meaning that one can never become consciously aware of these processes through any amount of introspection. Subconscious brain processes include those responsible for keeping the body alive, muscle reflexes, intuition, etc.

The brain is, in essence, a machine, and no machine can exist that would be completely self-aware. This is because any machine that has some level of self-awareness must have certain features that make self-awareness possible, and these features could not be subjectively understood by this same machine unless it had additional features that allowed it to understand its own self-awareness. It is easy to see how this leads to infinite regress and proves that no machine can be completely self-aware. The human brain is incredibly complex and there is a tremendous amount of the brain that humans will never be able to understand, even objectively. Any brain process can be at least partially understood through objective study, though because understanding itself requires brain capacity, no human can ever fully understand the human brain.

Despite the inherent limitations of the brain, subjective self-awareness is possible to some extent. It appears that the scope of knowledge that can be gained from introspection is limited to the following subjects:

The processes associated with sense data coming into the brain and then being interpreted. This includes when one sees an image, hears a sound, or receives data from any other senses. One who introspects should be able to understand the difference between different types of sense data and to understand which sense any datum comes from. This means that introspection should allow anyone to understand the difference between visual images and sounds and from this they should be able to take inventory of their senses. Although knowledge can be gained from the experience of introspection, this is not a sense, but a way of being consciously aware of brain processes that are not subconscious but that one’s central consciousness has a tendency to ignore unless one engages in introspection.

The processes associated with the generation of mental ideas that simulate sense data. This includes when one imagines a visual image, a sound, or a similar simulation of other senses. This can come either from memory or from mental synthesis. Any sane person should be able to know from introspection whether an idea came from a very recent sense experience, from memory, or from mental synthesis, at least most of the time.
The content of what one is currently thinking about. Most of the processes responsible for thoughts are subconscious, which effectively means that they are beyond the reach of introspection.

Introspection is made possible because the brain’s conscious awareness can direct its attention to any of the aforementioned subjects. Most of the time, the brain is not engaged in introspection and is thus tends to direct its attention to the content of sense data and to ongoing analysis of facts.