4.18 Here by the term 'non-action', the knowledge of the self, which is distinct from action and which forms the subject under consideration, is meant. 'He who sees non-action in action and also action in non-action,' denotes him who can perceive knowledge of the self even while action is being performed and who can also perceive action while engaged in non-action, i.e., knowledge of the self. What is the import of this saying?  What is taught here is this:  One can perceive, by constant contemplation on the truth about the self, that the action that is being performed in itself is a form of knowledge. One can also perceive that this knowledge is also of the form of Karma because of its being contained in Karma Yoga. Both these (i.e., action in the form of knowledge and knowledge in the form of actions) are accomplished by contemplation on the true nature of the self, even while work is being performed. Thus, he who can see actions as included in contemplation on the reality of the self, is wise, i.e., he knows the full meaning of the Sastras; he is fit among men, i.e., fit to attain release. He alone has fulfilled all actions, i.e., carried out the entire purpose of the Sastras. [The purport is that no contradiction between knowledge and action is felt by one who knows the philosophy of the self].

How is the form of knowledge accomplished through works which are obviously activities that are being performed?  Sri Krsna explains: