[Advaita-l] Gita 13.20 question

[mc1 at aol.com]

Namaste
Here's a selection from Gita 13.20 bhasya Gambhirananda tr.
How to explain Purusha, jiva and bhoktr described as synonymous? 



"So far as the agentship with regard to these is concerned Nature is said to be the cause, because of the same reason
of being their originator. As to how the soul can be the cause of mundane existence is being stated: Purusah, the soul, the empirical being, the knower of the field-all these are synonymous; is the hetuh, cause; bhoktrtve, so far as enjoyership, the fact of being the perceiver; sukha-duhkhanam, of happiness and sorrow-which are objects of experience, is concerned."