Out of the six traditional Indian schools of philosophy Sankhya is considered the oldest.

Its first principles appear in the Upanisads like Svetashvatara,Katha and Prashana. The System itself underwent modifications from time to time.  We have three strata of the system. The first is theistic and is represented by the Sankhya Pravachanasutra of Kapila.

The second is an atheistic system (not taking God into consideration) represented by Charaka and Panchashikha. The third and the most popular one is propagated by the Sankhya Karika of Ishvara Krishan. This also does not refer to God. It has  been commented upon by many scholars.

Sankhya enumerates 25 tattvas or principles and its chief objective is to effect the final emancipation of an individual soul (purusha) from the shackles of worldly existence. This is possible by acquiring the proper understanding of the other 24 tattvas and by discriminating between Purusha and Prakriti (primordial Matter) and its involutes .

Prakriti and Purusha are the two ultimate, independent tattvas, neither of which can be derived from each other. The whole universe owes its existence to the interaction between Prakriti and Purusha. The evolution of Prakriti can take place only through its contact with Purusha.

The philosophy of Sankhya is important for understanding the vedic scriptures such as the Upanisads and the Gita. It is also the basis for the Yoga system.