Vaiśeṣika's Doctrine of Validity.
The Vaiśeṣika system, like the Nyāya, recognizes two sources of valid knowledge:
Svataḥ-prāmāṇya (Intrinsic validity) is knowledge that is valid in itself, such as direct perception.
Parataḥ-prāmāṇya (Extrinsic validity) is knowledge that is validated by external factors, such as testimony or inference.
Thus, Vaiśeṣika places emphasis on extrinsic validation.