According to various Indian schools of philosophy, tattvas () are the elements or aspects of reality that constitute human experience. In some traditions, they are conceived as an aspect of deity. Although the number of tattvas varies depending on the philosophical school, together they are thought to form the basis of all our experience. The Samkhya philosophy uses a system of 25 tattvas, while Shaivism recognises 36 tattvas. In Buddhism, the equivalent is the list of dhammas which constitute reality, as in Nama-rupa. Etymology Tattva () is a Sanskrit word meaning 'thatness', 'principle', 'reality' or 'truth'. Hinduism Samkhya The Samkhya philosophy regards the Universe as consisting of two eternal realities: Purusha and Prakrti. It is therefore a strongly dualist philosophy. The Purusha is the centre of consciousness, whereas the Prakriti is the source of all material existence. The twenty-five tattva system of Samkhya concerns itself only with the tangible aspect of creation, theorizing that Prakriti is the source of the world of becoming. It is the first tattva and is seen as pure potentiality that evolves itself successively into twenty-four additional tattvas or principles. Shaivism In Shaivism the tattvas are inclusive of consciousness as well as material existence. The 36 tattvas of Shaivism are divided into three groups: Shuddha tattvas The first five tattvas are known as the shuddha or 'pure' tattvas. They are also known as the tattvas of universal experience. Shuddha-ashuddha tattvas The next seven tattvas (6–12) are known as the shuddha-ashuddha or 'pure-impure' tattvas. They are the tattvas of limited individual experience. Ashuddha tattvas The last twenty-four tattvas (13–36) are known as the ashuddha or 'impure' tattvas. The first of these is prakriti and they include the tattvas of mental operation, sensible experience, and materiality. Vaishnavism Within Puranic literatures and general Vaiśnava philosophy tattva is often used to denote certain categories or types of being or energies such as: Viṣṇu-tattva The Supreme God. The causative factor of everything including other Tattva(s). Kṛṣṇa-tattva Any incarnation or expansion of Śrī Narayan / Krishna. Śakti-Tattva The multifarious energies of Śrī Kṛṣṇa. It includes his internal potency, Yoga Maya, and material prakṛti. Jīva-tattva The living souls (jivas). Śiva-tattva Śrī Śiva (excluding Rudra(s)) is not considered to be a jiva. Mahat-tattva The total material energy (prakṛti). Gaudiya Vaishnavism In Gaudiya Vaishnava philosophy there are a total of five primary tattvas described in terms of living beings, which are collectively known as the