2.18 The root 'dih' means 'to grow.' Hence these bodies (Dehas) are characterised by complexity. They have an end - their nature is perishablity. For, jugs and such other things which are characterised by complexity are seen to have an end. The bodies of the embodied self, which are made of conglomerated elements, serve the purpose of experiencing the effects of Karmas, as stated in Brh. U. IV. 4.5, 'Auspicious embodiments are got through good actions.' Such bodies perish when Karmas are exhausted. Further the self is imperishable. Why?  Because it is not measurable. Neither can It be conceived as the object of knowledge, but only as the subject (knower). It will be taught later on:  'He who knows It is called the knower of the Field by those who know this (13.1).

Besides, the self is not seen to be made up of many (elements). Because in the perception 'I am the knower' throughout the body, only something other than the body is understood as possessing an invariable form as the knower. Further, this knower cannot be dismembered and seen in different places as is the case with the body. Therefore the self is eternal, for (1) It is not a complex being of a single form; (2) It is the knowing subject; and (3) It pervades all. On the contrary, the body is perishable, because (1) it is complex; (2) it serves the purpose of experiencing the fruits of Karma by the embodied self; (3) it has a plurality of parts and (4) it can be pervaded. Therefore, as the body is by nature perishable and the self by nature is eternal, both are not objects fit for grief. Hence, bearing with courage the inevitable strike of weapons, sharp or hard, liable to be received by you and others, begin the action called war without being attached to the fruits but for the sake of attaining immortality.