There are two natures. Just like you can understand, you are combination of two nature, the material nature and the spiritual nature. This gross body is material nature. It is made of earth, fire, water, air, ether, and mind, intelligence and ego. And the spiritual nature is yourself, the spirit soul, the living force, which is sustaining these material bodies. So both these natures, the material nature and the spiritual nature, they are different energies of God. Just like the fire has got two energies, namely, the heat and light, similarly, God has got two nature. One is called material nature and the other is called spiritual nature. So this cosmic manifestation which we experience is combination of material nature and spiritual nature. The material nature is called inferior nature, and the spiritual nature is called the superior nature. The material nature is inferior because the superior nature living entity controls over it. We have got experience. Just like a big machine, computer, or any other machine, it is combination of matter, but it cannot work independently until and unless there is touch of the spiritual nature, a human being. The big airplane is floating in the... (break) ...I mean to say, mechanical arrangement. But unless there is the pilot, it cannot work. Similarly, you try to understand that this material nature, cosmic manifestation, however wonderful it may be, unless there is direction of the Supreme Being, it is useless. So if you have understood the difference between material nature and the spiritual nature, then try to understand that as you have got experience of this material nature, there is another nature, another sky, another planetary system, everything another. That is all made of spiritual nature.
So that spiritual nature is described in the Bhagavad-gītā. You will get information. Paras tasmāt tu bhāvo 'nyo 'vyakto 'vyaktāt sanātanaḥ (BG 8.20). That nature is called sanātana. Sanātana means eternal. As we have got this body, your body, my body, or anyone's body, it is temporary, similarly, this material nature is temporary. Temporary means it has a beginning, it stays for some time, then it transforms, then it becomes old, and it vanquishes. The spiritual nature, however, is different from this nature. The spiritual nature has no beginning, neither it has end. That is called sanātana, eternal. We living entities, we belong to that spiritual nature. Therefore, about us, it is described in the Bhagavad-gītā, na jāyate na mriyate vā kadācit: "The spiritual spirit soul is never born, neither dies at any time." Nityaḥ śāśvato 'yaṁ na hanyate hanyamāne śarīre (BG 2.20). It is farther described that "This spiritual spark, which you are, I am, it is..." Na hanyate hanyamāne śarīre: (BG 2.20) "When the body is destroyed, the spiritual spark, that does not destroy. That remains eternal."
So it is a great science to understand what is that spiritual nature and what is that material nature, and we have published about eighty books of four hundred pages each for understanding what is this material nature and what is the spiritual nature. So at the present moment, the people, the whole human society, is missing this knowledge of spiritual nature. Therefore they are attached to this material nature, and here is a formula how we can become detached to this material nature and come to our original nature, spiritual nature. We are traveling all over the world, but there is no university, no institution, no school, no college where the education of spiritual nature is imparted. There is none. The greatest scientist, philosopher, they see that a man... A great scientist, great philosopher, they are working very nicely, but as soon as that spiritual nature is gone, this material nature body is useless.