SB 4.11.22

kecit karma vadanty enaṁ
 svabhāvam apare nṛpa
eke kālaṁ pare daivaṁ
 puṁsaḥ kāmam utāpare
Word for word: 
kecit — some; karma — fruitive activities; vadanti — explain; enam — that; svabhāvam — nature; apare — others; nṛpa — my dear King Dhruva; eke — some; kālam — time; pare — others; daivam — fate; puṁsaḥ — of the living entity; kāmam — desire; uta — also; apare — others.
Translation: 
The differentiation among varieties of life and their suffering and enjoyment is explained by some to be the result of karma. Others say it is due to nature, others due to time, others due to fate, and still others say that it is due to desire.
Purport: 

There are different types of philosophers — mīmāṁsakas, atheists, astronomers, sexualists and so many other classifications of mental speculators. The real conclusion is that it is our work only that binds us within this material world in different varieties of life. How these varieties have sprung up is explained in the Vedas: it is due to the desire of the living entity. The living entity is not a dead stone; he has different varieties of desire, or kāma. The Vedas say, kāmo ’karṣīt. The living entities are originally parts of the Lord, like sparks of a fire, but they have dropped to this material world, attracted by a desire to lord it over nature. That is a fact. Every living entity is trying to lord it over the material resources to the best of his ability.

This kāma, or desire, cannot be annihilated. There are some philosophers who say that if one gives up his desires, he again becomes liberated. But it is not at all possible to give up desire, for desire is a symptom of the living entity. If there were no desire, then the living entity would be a dead stone. Śrīla Narottama dāsa Ṭhākura, therefore, advises that one turn his desire towards serving the Supreme Personality of Godhead. Then desire becomes purified. And when one’s desires are purified, one becomes liberated from all material contamination. The conclusion is that the different philosophers’ theories to explain the varieties of life and their pleasure and pain are all imperfect. The real explanation is that we are eternal servants of God and that as soon as we forget this relationship we are thrown into the material world, where we create our different activities and suffer or enjoy the result. We are drawn into this material world by desire, but the same desire must be purified and employed in the devotional service of the Lord. Then our disease of wandering in the universe under different forms and conditions will end.