During the period of Gita, there emerged many schools of thought, or `Darshanas`, as they call them. Of these six of the schools became very famous. They are Gautama`s Nyaya, Kaanada`s Vaiseshika, Kapila`s Samkhya, Patanjali`s Yoga, Jaimini`s Purva Mimasa and Badarayana`s Uttara Mimamsa (or Vedanta). Although exact dates of the origin of these schools of thought are not known they are believed to have been formulated in sutras or aphorisms prior to Buddha.

There are certain common features to these systems: Firstly, they accept the authority of the Vedas, the feature that distinguishes them from philosophical schools of Buddhism and Jainism. Secondly, they represent a progressive development from lower to higher truth. All the systems are concerned with the nature of true Self.

1. Samkhya School of Philosophy:
Samkhya is the oldest among the philosophical systems and dates back to about 7c BC. Kapila, the author of `Samkhya Sutra", is considered to be the originator of this system. In the Smkhya school of Indian philosophy, Prakriti and purusha is refered as material nature and the soul. Prakriti is material nature in germinal state, eternal and beyond perception. When it comes into contact with the soul or purusha it starts a process of evolution that leads through several stages to the creation of the existing material world.There are no purely Samkhya schools existing today in Hinduism, but its influence is felt in Yoga and Vedanta schools of philosophy. The Hindu yoga schools are sometimes referred to as the `Samkhya -yoga schools`.

2. Yoga School of Philosophy:
Yoga is the way to achieve a pure body and a pure mind- the basic requirements of philosophy. In Yoga the ultimate unchanging perfect Purusha is termed god and if meditated upon he takes other purushas towards salvation. Patanjali`s Yogasutra is regarded as the main source of codification of yoga. Yoga is seen as a means to both physiological and spiritual mastery.

3. Nyaya School of Philosophy :
The Nyaya school of philosophical speculation is based on the oldest existing book, by Aksapada Gautama, known as the Nyaya Sutras. It is based on the theme of knowledge and logical analysis.Nyaya deals with knowing. It has sixteen categories, dealing with the means to understand the universe.

4. Vaisheshika School of Philosophy:
Nyaya and Vaiseshika are considered sister philosophies. Both state that by leading virtuous life and remaining on the side of Dharma, one will have both growth and fulfillment in life (Abhyudaya) as well as realization of the highest good - Liberation (Nishreyasa). These systems are dualistic in their conception of God (Supreme Self), Jiva (individual self), and the universe.

5. Purva Mimamsa School of Philosophy:
Purva Mimamsa is earlier (purva) to Uttara (later) Mimamsa in a logical sense. The word Mimamsa means to analyze and understand thoroughly. By the Sutra period the Vedas were beginning to lose their glory in public opinion hence some scholars began to reanalyse the Vedas in order to defend them and justify Vedic ritualism. Mimamsa is to investigate Dharma (duty) as given in the Vedas. Purva Mimamsa examines the teachings of the Veda in the light of karma-kanda rituals.

6. Uttar Mimansa School of Philosophy ( Vedanta)
The Vedanta philosophy is important both for its philosophical views and its close connections with the existing Hinduism. Uttara Mimamsa (also called Vedanta Sutra or Brahma Sutra) of Badarayana deals with the Brahman doctrine. It consists of 555 sutras. Vedanta bases its many observations and explanations on Samkhya system.