On this earth planet we see change of day and night and of seasons. The more primitive mentality attributes this change to changes occurring in the sun. For example, in the winter they think the sun is getting weaker, and at night they presume sometimes that the sun is dead. With more advanced knowledge of discovery we see that sun is not changing at all in this way. Seasonal and diurnal changes are attributed to the change of the position of the earth planet.
Similarly, we experience bodily changes, from embryo to child to youth to maturity to old age and to death. The less intelligent mentality presumes that at the death the spirit soul's existence is forever finished, just like primitive tribes who believe that the sun dies at sunset. Actually, the sun is rising in another part of the world. Similarly, the soul is accepting another type of body. When the body gets old like the old garments and is no longer usable, then the soul accepts another body, just like we accept a new suit of clothes.
The modern civilization is practically unaware of this truth. They do not care about the constitutional position of the soul. There are different departments of knowledge in different universities and many technological institution to study and understand the subtle laws of material nature, medical research laboratories to study the physiological condition of the material body, but there is no institution to study the constitutional position of the soul.
This is the greatest drawback of material civilization, which is external manifestation of the soul. They are enamored by the glimmering manifestation of the cosmic body or the individual body, but they do not try to understand the basic principles of this glimmering situation. The body looks very beautiful, working with full energy and exhibiting great traits of talent and wonderful brain work. But as soon as the soul is away from the body, all this glimmering situation of the body becomes useless.
Even the great scientists who have discovered many wonderful scientific contributions could not trace out about the personal self, which is the cause of such wonderful discoveries. The Kṛṣṇa consciousness movement basically is trying to reach this science of the soul—not any dogmatic way, but in complete scientific and philosophical understanding.
You can find out the background of this body as the soul and the soul's presence as perceived . . . perceivable by consciousness. Similarly, the presence of Supersoul and superconsciousness in the universal body of cosmic manifestation is perceived by the presence of the Supreme Lord, or the Absolute Truth.
The Absolute Truth is systematically experienced in the Vedānta-sūtra, generally known as the Vedānta philosophy, which is elaborately explained by a commentary by the same author of the Vedānta-sūtras known as the Śrīmad-Bhāgavatam. The Bhagavad-gītā is the preliminary study of the Śrīmad-Bhāgavatam to understand the constitutional position of the Supreme Lord, or the Absolute Truth.