The living entity is a spiritual soul, and the material body is his encagement. This is the beginning of spiritual understanding.
- dehino 'smin yathā dehe
- kaumāraṁ yauvanaṁ jarā
- tathā dehāntara-prāptir
- dhīras tatra na muhyati
"As the embodied soul continually passes, in this body, from boyhood to youth to old age, the soul similarly passes into another body at death. The self-realized soul is not bewildered by such a change." (BG 2.13) The real mission of human life is to get free from encagement in the material body. Therefore Kṛṣṇa descends to teach the conditioned soul about spiritual realization and how to become free from material bondage. Yadā yadā hi dharmasya glānir bhavati bhārata (BG 4.7). The words dharmasya glāniḥ mean "pollution of one's existence." Our existence is now polluted, and it must be purified (sattvaṁ śuddhyet). The human life is meant for this purification, not for thinking of happiness in terms of the external body, which is the cause of material bondage. Therefore, in this verse, Mahārāja Yayāti advises that whatever material happiness we see and whatever is promised for enjoyment is all merely flickering and temporary. Ābrahma-bhuvanāl lokāḥ punar āvartino 'rjuna (BG 8.16). Even if one is promoted to Brahmaloka, if one is not freed from material bondage one must return to this planet earth and continue in the miserable condition of material existence (bhūtvā bhūtvā pralīyate) (BG 8.19). One should always keep this understanding in mind so as not to be allured by any kind of sense enjoyment, in this life or in the next. One who is fully aware of this truth is self-realized (sa ātma-dṛk), but aside from him, everyone suffers in the cycle of birth and death (mṛtyu-saṁsāra-vartmani (BG 9.3)). This understanding is one of true intelligence, and anything contrary to this is but a cause of unhappiness. Kṛṣṇa-bhakta-niṣkāma, ataeva 'śānta.' (CC Madhya 19.149) Only a Kṛṣṇa conscious person, who knows the aim and object of life, is peaceful. All others, whether karmīs, jñānīs or yogīs, are restless and cannot enjoy real peace.