Nyāya Sūtras 2.3

2.3

pramāṇam antareṇa nārthapratipattiḥ, nārhtapratipattim antareṇa pravṛttisāmarthyam/ pramāṇena khalv ayaṃ jñātārtham abhīpsati jihāsati vā/ tasyepsājihāsāprayuktasya samīhā pravṛttir ity ucyate/ sāmrthyaṃ punar asyāḥ phalenābhisambandhaḥ/ samīhamānas tam artham abhīpsan jihāsan vā tam artham āpnoti jahāti vā/ arthas tu sukhaṃ sukhahetuś ca, duḥkhaṃ duḥkhahetuś ca/

Without a means of valid cognition there is no comprehension of an object; without the comprehension of an object there is no efficacy of activity. For it is through a means of valid cognition that a person, having cognized an object, desires to obtain it or desires to avoid it. The exertion of one who is motivated by the desire to obtain or to avoid is called activity. Its 'efficacy', in turn, is its connection with the result: exerting oneself, desiring to obtain or desiring to avoid that object, one obtains that object or avoids it. And the object is pleasure and the cause of pleasure, and pain and the cause of pain.