While the psychology of the human personality is important for both personal and social life in the world, it also follows that, for purposes of psychology, the individual stands segregated from the world of perception. Viewed in this light, the human individual can be studied as a composite structure of different layers of the constitutional makeup, these layers being, broadly speaking, the well-known physical, vital, sensory, mental, intellectual, causal, and spiritual realms of inclusiveness and intensity. The physical body is the outermost crust, we may say, of the person, and it is constituted of the very same stuff as the earth, water, fire, air and ether of the physical world. The chemical components of which the body is made are just proportionate mixtures, permutations and combinations of these elements that are entirely physical in nature. There is nothing in the body except elements of solid matter, liquid, gas and heat, with space providing the volume of the body. The intake of diet maintains this body, fattens it by energising it with the subtle forces generated through the digestion of food, which permeate the entire body in its various systems like the circulatory, respiratory, alimentary, etc.

But, there is something inside, within the physical body, which gives and meaning to the body, namely, the vital system, known as the operation of the Prana, which is an energy quantum distributed equally throughout the body, giving it strength as if by the passing of an electric current through every pore and cell of the system. In fact, the life of the body is just the life imparted to it by the Prana. That part of the body which the Prana does not touch gets paralysed and is virtually dead. This means that the physical body by itself has no life, the life principle being the Prana, entirely. The Prana is said to function in five ways, and according to this fivefold function, the total energy of the Prana goes by the names of Prana, Apana, Vyana, Udana and Samana. Prana is the force that ejects the breath out in exhalation. Apana is what pulls the breath within in inhalation. Vyana is the circulatory force which causes the equidistribution of blood through the blood vessels spread out through the body. Samana is the energy of heat that digests food in the stomach. Udana takes one to the state of deep sleep and also is said to cause the separation of the true person from the body at the time of death.

But, what causes the Prana to act in this manner in relation to the physical body? The answer is, the action of the mind working through the sense organs, namely, seeing, hearing, touching, tasting and smelling. The mind performs four functions, as Manas, or indeterminate thinking; Buddhi, or determinate and discriminative thinking; Chitta, or memory and remembrance; and Ahamkara, or the ego principle which asserts and arrogates to itself the self-identity of human individuality through all its layers, right from the physical to the causal. The necessity and the desire of the mind working through the sense-organs to dwell in the physical body for fulfilling its own purposes causes a tremendous pressure exerted on the whole body, this pressure being called the Prana. The Prana, thus, is a sort of link between the physical body and the internal organ, the psyche. The faculties of feeling and emotion in all their variety are characteristic of the mind-stuff, the psychic organ.

The ratiocinating, discriminating, deciding, and logically, judging faculty is at the higher level and is known as the Buddhi, or the pure understanding. It is this faculty that draws conclusions on a consideration of pros and cons of situations, by inference, either deductively or inductively. This is the realm of reason which has a dual aspect, namely, the lower and the higher. The lower reason, which is the one that mostly operates in all human individuals, is that operation which just collects the reports and evidences supplied by the mind through the sense organs, arranges them into a pattern of wholeness and passes a judgment on the nature of these sensory evidences. This would mean that the judgment of the lower reason is not qualitatively different from the reports of the sense organs, and its judgment is virtually the judgment of the sense organs arranged into a system of apparent collectivity, totality uniqueness and unity. But, the higher reason is something like an ambassador operating between the consciousness of human individuality and the possibilities ranging beyond the individual and its operations. This superior reason can infer the existence of wider realities of an infinite nature by various observations, like the necessity to posit a cause behind all effects, the need to accept a limitless state of existence on the perception of limitation and finitude in one's life, the need to posit an Architect of the universe on the basis of the fact of the system, method and precision as well as symmetrical action observable in the working of nature, and the like. These are some of the ways which the higher reason adopts necessarily on account of its very constitution in creating an aspiration in the individual to rise from the consciousness of particularity to that of Universal Being. The higher reason is the true philosopher and repository of the wisdom of life.

The intermediary sheath between the intellect and the fundamental self-consciousness is constituted of an unconscious layer containing all the potentials of future experiences through a repetition of dream and waking lives, the well-known cycle of metempsychosis. This causal layer of potential future experience is the seed that can germinate into varieties of individualised experiences through continuous births and deaths. What are known as the conscious mind and the subconscious level, etc., form just a fraction of the storehouse of potentials which constitute the stuff of the unconscious. Since even the intelligence of the intellect and the mind is only that quality of knowledge which is permitted by the unconscious realm to pass through its own special modification as the intellect, it would be perhaps very true to say that all worldly knowledge which is intellectual, mental and sensory is a form of ignorance.