Isvara (the Supreme Lord), jiva (the living entity), prakriti (nature), kala (eternal time) and karma (activity) are all explained in the Bhagavad-gita. Out of these five, the Lord, the living entities, material nature and time are eternal. The manifestation of prakriti may be temporary, but it is not false. Some philosophers say that the manifestation of material nature is false, but according to the philosophy of Bhagavad-gita or according to the philosophy of the Vaishnavas, this is not so. The manifestation of the world is not accepted as false; it is accepted as real, but temporary. It is likened unto a cloud which moves across the sky, or the coming of the rainy season, which nourishes grains. As soon as the rainy season is over and as soon as the cloud goes away, all the crops which were nourished by the rain dry up. Similarly, this material manifestation takes place at a certain interval, stays for a while and then disappears. Such are the workings of prakriti. But this cycle is working eternally. Therefore prakriti is eternal; it is not false. The Lord refers to this as “My prakriti.” This material nature is the separated energy of the Supreme Lord, and similarly the living entities are also the energy of the Supreme Lord, although they are not separated but eternally related. So the Lord, the living entity, material nature and time are all interrelated and are all eternal. However, the other item, karma, is not eternal. The effects of karma may be very old indeed. We are suffering or enjoying the results of our activities from time immemorial, but we can change the results of our karma, or our activity, and this change depends on the perfection of our knowledge. We are engaged in various activities. Undoubtedly we do not know what sort of activities we should adopt to gain relief from the actions and reactions of all these activities, but this is also explained in the Bhagavad-gita.