1. The Vedantist Philosophy may be described as a mystico-idealistic Monism; the Sankhya on the other hand (of which Capila is said to be author) is a well-marked Dualism. According to the Sankhya, all that exists is either producing and not produced, or at once produced and producing, or produced and not producing, or finally neither produced nor producing.
(a.) What produces without being produced is Nature (Prakriti) natura naturans, -- the ultimate basis of all material things, a subtle but yet a corporeal substance.
(b.) What produces and is produced is Reason (Buddhi), the Reason of nature, its rational condition.
(c.) What is produced without producing is Self-consciousness (Ahankara), the basis of the Ego.
(d.) What is neither producing nor produced, is the Soul, the spirit (Puruscha).
2. Of the four members of this division, the first and last, Nature and Spirit -- stand farthest apart, while the intermediate members form a connecting link between them, and are dependent on them.
Nature -- Prakriti, is uncreated, eternal, but wholly blind, working without consciousness and without knowledge. It is a single principle, by the forces inherent in which is evolved everything that we find in the material world.
Next comes Reason -- Buddhi. This reason is not something raised above nature; it is something indwelling in it. It manifests itself in the purpose visible in all nature's works. It is the rational element in nature, nature itself being merely matter.
From Nature and Reason is further evolved Consciousness (Ahankara). By this is not meant the pure Ego, eternally self-knowing -- the spirit in itself, but rather that Ego which is always studiously asserting itself, that more or less empty consciousness, that spontaneity in which the wavering reason seeks to establish for itself a centre for the relations created by its activity. Ahankara is the groundwork of Avarice and Pride; through it all evil comes into the world. Ahankara is furthermore the principle in man on which depend the internal Sense, the understanding (Manas), the organs of sensation and movement, and the bodily condition in general. By the term Ahankara, Sankhya would seem to signify a kind of brute soul.
Above Nature thus developed, and essentially differing from it stands the Soul -- Puruseha. Sankhya proves the existence of a soul distinct from nature in this wise: --
(alpha.) We find an organic formation existing in blind material nature, such a formation as we may compare to a workman's instrument. This implies the existence of something else for whose benefit the instrument exists. This something else must be a being of knowledge -- a soul. As there exists an object to be made use of, there must exist a being to use it; this being is the soul.
(beta.) Again, the effort after supreme happiness supposes an abstraction which rises above the passing world, the world of sense. This effort, which we recognise in ourselves, is proof of the existence of a soul, for the soul alone is capable of such abstraction.
(gamma.) Lastly, the members of an antithesis mutually suppose one another. From the existence of a force in nature exercised in blind, unreasoning outward action, we may argue the existence of an intelligent self-contained soul.
3. From what has been said, it is now apparent in what relation the two members of the antithesis -- Nature and Soul -- stand to one another. The principle of all activity and all motion is Nature, and Nature alone. The Soul is neither active nor productive, it is merely a tranquil spectator of what goes on in Nature. There are, however, mutual dependences between them. Nature, as a blind principle of action, can have no purpose in itself, it can exist only for something else, for something which is intelligent; Nature, then, exists for the Soul. On the other hand, the Soul cannot, apart from Nature, attain to knowledge, especially to the knowledge of itself as of something distinct from Nature. They are to one another as the blind and the lame; the Soul has no power of movement or action, Nature cannot see the way before it; the one supplies what is wanting to the other, and from both together arises the whole order of spiritual and material phenomena.
4. Sankhya does not make the Soul a single principle as it makes Nature; it admits a plurality of souls. "This it takes to be proved by the fact, that different destinies befall souls; that different pains and pleasures are experienced by them; that they are engaged in different occupations." We have also to distinguish in man between the subtle body -- Linga, and the gross material body by which the former is enveloped. The former consists of Buddhi (Reason), Ahankara, Manas, the ten senses, and the five subtle elements. The Linga has not in itself a personal character, it attains this perfection in virtue of its union with the Soul, to which it is united until the latter is finally emancipated.
5. With regard to the duty of man in life, Sankhya makes the deliverance of the Soul (from the trammels of Nature) the highest end of all human effort. And here, too, "knowledge" is the means by which deliverance is accomplished. Human works avail nothing. The required knowledge consists in this, that the Soul apprehends the essential difference between itself and Nature. "Deliverance" is no more than the divesting of the Soul, by right knowledge, of that which belongs to it in appearance only, and which hides it from the eye of sense. All that happens in Nature, happens that the Soul may attain this self-knowledge, this view of its own being.
6. When the Soul has reached this term; when it has attained the conviction that nothing of all that happens in the world is its work, or its concern, it is freed thereby from earthly disquiet, from all the influences, and hampering forces of Nature. It may still remain in union with the body, just as the potter's wheel continues to revolve, though it is no longer in use; but the movements of the body no longer trouble the Soul, they can be of no further use to it. Prakriti, like a dancing girl, presents itself before Puruseha to lead it to knowledge, and then modestly withdraws when the task is finished. If deliverance is not complete in this life, it will be perfected after death, and the man who has attained it, is exempted from those transmigrations to which other souls are subject.
7. Connected with Sankhya, and probably an offshoot from it, is the philosophical system of Yoga. Respecting this system, we have little detailed knowledge. It is to a great extent in accord with Sankhya, but it differs from it in this, "that it admits a supreme God, ruler of all things, who is a Spirit or Soul, distinct from other souls, untroubled by the evils to which they are subject, free from good and free from evil deeds and their consequences, infinite, eternal, omniscient." What relations Yoga established between this God and the world we do not know. It may have been the object of the teaching of Yoga to set up a Divinity which should unite in one being the elements Nature and Soul, so sharply contrasted in Sankhya.