Sāṃkhya, which is one of the oldest systems (darśana) of Indian Philosophy, advocates an uncompromising dualism in its theoretical metaphysical teachings. There is a fundamental dualism or split at the very heart of reality, and this dualism or split is the fundamental fact of existence.According to Sāṃkhya, there are two co‑present and co‑eternal realities. The first one is the principle of pure Consciousness, the Puruṣa, which is inactive, indifferent, eternally free and Alone. Puruṣa is the soul, the self, the spirit, the subject, the knower. The other of the two co‑present and co‑eternal realities of Sāṃkhya is Nature or Prakṛti : it is the primordial and unconscious “stuff ” of the entire unmanifest and manifest world, whereas Puruṣa is the presupposition of individual consciousness. Nature or Prakṛti is the ultimate material principle and thus the substratum from which manifest, in the presence of the self (puruṣa), the gross and subtle bodies including the mental organs of all living beings. But Sāṃkhya is not a dualism of mind and body or even a dualism of subject and object.In classical Sāṃkhya the world is not derived from consciousness, nor is consciousness derived from the world. The classical Sāṃkhya refuses to understand the world simply as a product of consciousness. It refuses to see the world as an illusory projection of consciousness, and thus it rejects any idealistic monism. Similarly, it refuses to see consciousness simply as a product of the world, and thus it rejects any kind of materialism or naturalism. Thus, it steers an intermediate course or path between the Indian notion of a conscious, cosmic Self or its equivalent, which is the ground of all being, on the one hand, and the notion of a conscious self, which is only an empirical, relative construction, on the other. It maintains, rather, a fundamental dualism, the opposite poles of which function in a kind of dialectical interaction. The fact of consciousness and the fact of the world are two irreductible realities in constant interplay with one another. Though quite separate and unconnected, Spirit and Nature mutually interact to bring about the process of creation, self‑awareness and, finally, enlightenment. But Spirit or Puruṣa and Nature or Prakṛti are always only in proximity to one another, never in actual contact. This is a puzzling notion if one thinks of Puruṣa and Prakṛti as two things. Puruṣa and Prakṛti are two realities of a completely different order.Right knowledge is the knowledge of the separation of the Puruṣa from the Prakṛti. The individual soul (jīva) has to realize itself as the pure Puruṣa through discrimination between Puruṣa and Prakṛti.From a rational point of view, classical Sāṃkhya can be regarded as a bundle of contradictions. Some problems regarding its interpretation are the problem of the nature of the Sāṃkhya dualism and the problem of the connection or relationship of Puruṣa and Prakṛti. The Sāṃkhya system clings to spiritualistic pluralism and dualistic realism, but its very logic indeed impels it to embrace idealistic monism or absolutism.