One who walks on the spiritual path and who wants to attain the highest Truth should not depend on any external motivation to act. Most people are distracted by the temporary temptations of life and forget the very purpose of their lives.

jñāna (knowledge) teaches us how to develop vairāgya (detachment). vairāgya without jñāna is like one who blindly follows and acts, potentially discarding the right things in life instead of the wrong things. jñāna tells one that from the temporary, permanence cannot be attained. vairāgya helps one discard all outward desires. 

The relationship between jñāna and vairāgya enables one to ultimately realise the Truth.