Nyāya philosophers, a theistic realist school, offer several proofs for the existence of God (Īśvara) primarily through inference (anumāna), viewing Him as the efficient cause of the universe.

1. Kāryatva (Argument from Causality/Effects): This is the most prominent proof. Nyāya argues that the entire universe (kārya) – with its order, design, and systematic arrangement – is an effect. All effects must have an intelligent, efficient cause (Nimitta Kāraṇa). An unconscious cause (like Sāṃkhya's Prakriti) cannot produce an intelligent effect. Therefore, an omniscient, omnipotent, and intelligent being, Īśvara, must be the ultimate efficient cause of the world.

2. Dhṛtyādyaytanāt (Argument from Sustenance and Dissolution): The orderly maintenance (dhṛti) and systematic destruction (pralaya) of the universe cannot be accidental. This continuous, purposeful activity implies an intelligent sustainer and destroyer, who is Īśvara.

3. Vākya-pramāṇa (Argument from Verbal Testimony/Scriptural Authority): Nyāya accepts the Vedas as infallible verbal testimony. The authoritative nature and consistency of Vedic injunctions regarding dharma and adharma imply an intelligent, omniscient author – Īśvara – who is the ultimate source of this valid knowledge.

4. Pramāṇatvāt (Argument from Valid Knowledge): The validity of all other pramāṇas (perception, inference) ultimately depends on an original, ultimate knowledge source, which is God.

These arguments collectively aim to establish Īśvara as the supreme, intelligent architect and sustainer of the cosmos.