The philosophy of self defines, among other things, the conditions of identity that make one subject of experience distinct from all others. Contemporary discussions on the nature of the self are not thereby discussions on the nature of personhood, or personal identity. The self is sometimes understood as a unified being essentially connected to consciousness, awareness, and agency (or, at least, with the faculty of rational choice). Various theories on the metaphysical nature of the self have been proposed. Among them, the metaphysical nature of the self has been proposed to be that of an immaterial substance.
Most philosophical definitions of self—per Descartes, Locke, Hume, and William James—are expressed in the first person. A third person definition does not refer to specific mental qualia but instead strives for objectivity and operationalism.
To another person, the self of one individual is exhibited in the conduct and discourse of that individual. Therefore, the intentions of another individual can only be inferred from something that emanates from that individual. The particular characteristics of the self determine its identity.
In spirituality, and especially nondual, mystical and eastern meditative traditions, the human being is often conceived as being in the illusion of individual existence, and separateness from other aspects of creation. This "sense of doership" or sense of individual existence is that part which believes it is the human being, and believes it must fight for itself in the world, is ultimately unaware and unconscious of its own true nature. The ego is often associated with mind and the sense of time, which compulsively thinks in order to be assured of its future existence, rather than simply knowing its own self and the present.