Samkhya is a school of Indian philosophy that is based on the concept of dualistic realism. It explains the relationship between spirit and matter through the principles of Purusha and Prakriti.

According to Samkhya, Purusha refers to the pure consciousness or spirit, whereas Prakriti refers to the material world or matter. These two entities are seen as distinct and separate from each other, yet they are interconnected and interdependent.

Purusha is considered to be the source of all consciousness and awareness. It is eternal, unchanging, and unaffected by the material world. On the other hand, Prakriti is the source of all material existence. It is made up of three basic qualities or "gunas" - Sattva (purity), Rajas (activity), and Tamas (inertia).

The relationship between Purusha and Prakriti is described as that of a witness and the witnessed. Purusha, being pure consciousness, is the passive observer of Prakriti and its manifestations. It is not involved in the workings of the material world, but simply witnesses it.

Prakriti, on the other hand, is constantly in a state of flux, creating and transforming the material world. It is driven by the three gunas, which are responsible for the diversity and complexity of the material world. This constant activity of Prakriti is what gives rise to the illusion of the material world and keeps Purusha bound to it.

Samkhya also explains that the interaction between Purusha and Prakriti is what leads to the creation and evolution of the universe. When Purusha becomes aware of Prakriti, it becomes the "knower" and Prakriti becomes the "known". This awareness leads to the manifestation of the material world.

However, despite their interdependence, Purusha and Prakriti are seen as distinct and separate entities. Purusha is considered to be the ultimate reality, while Prakriti is seen as a mere reflection of Purusha. It is through the understanding of this relationship that one can attain liberation from the material world and achieve union with Purusha.

In conclusion, Samkhya explains the relationship between spirit and matter as that of a passive observer and an active creator. The two entities are interconnected and interdependent, yet distinct and separate. It is through the understanding of this duality that one can attain liberation and transcend the material world.