Read this: In its metaphysics, Nyāya school is closer to the Vaiśeṣika school than others. It holds that human suffering results from mistakes/defects produced by activity under wrong knowledge (notions and ignorance). Moksha (liberation), it states, is gained through right knowledge. This premise led Nyāya to concern itself with epistemology, that is the reliable means to gain correct knowledge and to remove wrong notions. False knowledge is not merely ignorance to Naiyayikas, it includes delusion. Correct knowledge is discovering and overcoming one's delusions, and understanding true nature of soul, self and reality. The Nyāya Sūtras begin:

What philosophy produces human suffering?
What is the answer? (If it cannot be answered, return "unanswerable")
unanswerable