Self-awareness is the capacity for introspection

Introspection

Introspection is the self-observation and reporting of conscious inner thoughts, desires and sensations. It is a conscious and purposive process relying on thinking, reasoning, and examining one's own thoughts, feelings, and, in more spiritual cases, one's soul...

 and the ability to reconcile oneself as an individual separate from the environment and other individuals. Self-awareness, though similar to sentience

Sentience

Sentience is the ability to feel, perceive or be conscious, or to have subjective experiences. Eighteenth century philosophers used the concept to distinguish the ability to think from the ability to feel . In modern western philosophy, sentience is the ability to have sensations or experiences...

 in concept, includes the experience of the self

Self

The self is an individual person as the object of his or her own reflective consciousness. The self has been studied extensively by philosophers and psychologists and is central to many world religions.-Philosophy:...

, and has been argued as implicit to the hard problem of consciousness

Hard problem of consciousness

The hard problem of consciousness is the problem of explaining how and why we have qualitative phenomenal experiences. David Chalmers contrasts this with the "easy problems" of explaining the ability to discriminate, integrate information, report mental states, focus attention, etc...

.
While reading Descartes, Locke began to relish the great ideas of philosophy and the scientific method. On one occasion, while in a meeting with friends, the question of the "limits of human understanding" arose.