Nityanitya padartha refers to the constant and changeable entities in Hindu philosophy. While classifying the entities under nityanitya padartha, Madhavacharya points out the peculiar nature of some padarthas. This is discussed in Tattvasankhyana, Isavasya Bhashya, etc.
The entities are broadly classified as independent and dependent. The independent entity is Bhagavan Vishnu. He is constant (nityo nityanam). Out of the dependents all cetanas (animates) are eternal.
The acetanas (inanimate) are classified into three categories:
- Nitya (eternal),
- anitya (ephemeral),
- nitya anitya (having dual nature).
Nitya (eternal) – Vedas. These are unauthored texts. They are beginningless and eternal. Even in the total deluge (pralaya), Vedas are retained by Vishnu as part of his wisdom. He reveals them again at the beginning of a new kalpa. Similarly, varna letters (Ka, Ga, Ya, etc.) are eternal. Avyakrta akasha (eternal space) is entirely different from ethereal space, which is subjected to change. Eternal space never undergoes any change at any time.
Anitya (ephemeral) – This is of two types – samrsta (wholly created) and asamrsta (partially created). The cosmic egg and its contents are wholly created. This is an effect. At the time of the total deluge (maha pralaya), the effect, i.e., the cosmic egg and its contents get reconverted into causal matter. The partially created matter is the derivative of primordial matter (mula prakriti). The derivatives are mahat, ahamkara, intellect, mind, ten organs and five elements, totaling twenty four. This is asamsrsta. Only a part of it is used in creating the cosmos and its contents. Asamrsta forms the material cause of the universe.
Nitya-anitya (dual-nature) – Puranas – Their meanings are eternal, but as texts they are ephemeral. The original prakriti (mula prakriti) is eternal, but modified into different forms it is non-eternal. The eternal flow of time (maha kala) is eternal, but fractional time (atomic) is ephemeral.