The Samkhya system is dualistic in its ontology. It believes in two ultimate realities – prakriti and Purusa. The entire manifested world, both material and mental, with all its objects and processes, is regarded as transformation of prakriti the Primordial Substance, the original stuff of all that there is amn and universe except the Purusas or the Selves which the independently real.

The prakriti is constituted by a triad of fundamental attributes (Gunas) – Sattva, Rajas and Tamas, the basic causes of though, movement, and inertia. All modifications or transformations of these Gunas.

        The Purusa becoming active and the prakriti becoming conscious as it were. Purusas are infinitely many one behind each individual. They are eternal. The prakriti works purposively for the enjoyment and release of the Purusas. it is all in all and works itself without any guidance from God, who is not required in the system for any purpose whatsoever. The Purusa in bondage gets released by the efforts of prakriti in the form of Buddhi (intelligence) which, when purified by moral action and metaphysical thinking, gives rise to discrimination (Viveka) in the Purusa. The released Purusa is free from all sufferings and stays in the form of pure consciousness.

The Yoga system is more or less applied Samkhya. It has devised a systematic method of bringing about the release of Purusa from Prakrti by purifying and controlling and ultimately nullifying the modification of the mental mechanism (antahkarana or citta) and thereby letting the Purusa stand and shine in its own pristine purity.

The method is called the Ashtanga Yoga which consists in the practice of Yama (Self-control), Niyama (observance of certain principles), Asana (fixed postures of the body) Pranayama (breath-control), Pratyahara (withdrawal of the senses and the mind from the objects of enjoyment), Dharana (fixation of mind on some chosen object), Dhyana (controlled and continued attention to the object) and Samadhi (mergence of the mind in some object and then dissolution of it in the Self). In the state of Samadhi, the Purusa gets its own experience and realizes its true nature.

The Yoga system admits the existence of God as an eternally freed Purusa, who is the teacher and guide of Yoga and on being invoked can help those who practice Yoga.

        The Mimamsa system is not really a philosophy in the sense of tacking ontological, epistemological, cosmological, archaeological or theological questions freely and logically on the basis of one’s experience and observation. It is a philosophy of interpretation, application and use of texts of the Samhita and Brahmana portions of the Vedas. It has devised certain principles according to which the Vedic mantras and their application in the field of sacrifices (yajnas) could be understood in a systematic manner.

        Ancient Indian though reached its culmination in the philosophy of Shankaracharya. Sankara wrote a large number of works including his well-known commentaries on the Upanishads, the Brahma Sutras and the Bhagavad-Gita. The philosophical views in his writings came to be known as Advaita Vedanta. The word Vedanta originally meant the Upanishads, the last (anta) portions of the Vedas.

The Brahma Sutras of Badarayana testify to an attempt at synthesizing and systematizing the teachings of the Upanishads. The Bhagavad-Gita is said to present the essence of the thought of the Upanishad and also goes by the name of Upanjad. Hence the views in Sankara’s commentaries on these three works, namely, the Upanishads, the Brahma Sutras and the Bhagavad Gita constitute Vedanta Philosophy (Vedanta Darsana).

As Sankara held that all these works teach that the Ultimate Reality is One, Only One, and without a second by its side, the Vedanta philosophy impounded by him goes by the name of Advaita (Secondless) Vedanta.

        The Ultimate Reality, according to the Advaita Vedanta, is Brahman. The Brahman is the cause of the world and is changeless within itself. All the attributes that we ascribe to Brahman are conceived from our own points of view.

The world as a whole, and in all its parts, shows signs of purposiveness, intelligence and organization and, therefore, presupposes a Creator and Governor. This creator is God (Ishvara) or a cosmic form of the Absolute Brahman. He creates a particular world order out of Himself, like a spider spinning a web, and governs it justly in accordance with the ‘Law of Karman’ which is the expression of his own will for justness and impartiality.

He is not a Second reality to the Brahman. He is the Brahman limited or associated by its own Creative Power, which brings forth the world of plurality from within itself. This power is called Maya. The world comes out of it as a tree comes out of the seed.