Samkhya is a philosophical system that originated in ancient India and is based on the concept of dualistic realism. It explains the world through the concept of duality between Purusha and Prakriti.

According to Samkhya, Purusha refers to the eternal, pure consciousness or spirit, while Prakriti refers to the material world and all its components. These two are considered to be the fundamental principles of existence, and everything in the world can be explained through their interaction.

The concept of duality in Samkhya is based on the understanding that Purusha and Prakriti are distinct and independent entities. They are not dependent on each other for their existence, but they are in constant interaction and influence each other.

Purusha is considered to be the passive observer and witness of Prakriti. It is the unchanging, eternal consciousness that remains unaffected by the changes in the material world. Prakriti, on the other hand, is the active force that creates, sustains, and destroys everything in the material world. It is made up of three gunas or qualities – sattva (purity), rajas (activity), and tamas (inertia).

The duality between Purusha and Prakriti is also reflected in the individual human beings. According to Samkhya, every individual has a combination of Purusha and Prakriti within them. The Purusha is the true self or the soul, while the Prakriti is the physical body and the mind. The mind, which is a part of Prakriti, is responsible for the perception of the world and the individual's actions.

Samkhya explains the concept of duality through the theory of evolution. It states that the material world, or Prakriti, evolves from its unmanifested state to its manifested state through the interaction of the three gunas. This evolution is driven by the desire of Purusha to experience the material world.

However, according to Samkhya, the ultimate goal is to transcend this duality and realize the true nature of Purusha. This can be achieved through self-realization and detachment from the material world.

In conclusion, Samkhya explains the concept of duality through the interplay of Purusha and Prakriti. It sees the world as a manifestation of the interaction between these two distinct but inseparable entities. The understanding of this duality is essential for individuals to transcend it and attain spiritual liberation.