Chapter IV Sloka 18

kmR{ykmR y> pZyedkmRi[ c kmR y>,
s buiÏmaNmnu:ye;u s yu­> k«TõkmRk«t!

karmaõyakarma ya× paþyed
akarmaõi ca karma ya× |
sa buddhim˜nmanuÿyeÿu sa 
yukta× k®tsnakarmak®t ( 4|18)||

He who sees inaction in action and action in inaction, he is wise among men; he is a Yogi and performer of all actions.


In common parlance, action means ‘movement of the body, movement of the hands and feet’, and inaction means ‘to sit quiet’.
It is the idea of agency, the idea 'I am the doer' that binds man to Samsara. If this idea vanishes, action is no action at all. It will not bind one to Samsara. This is inaction in action. If you stand as a spectator or silent witness of Nature’s activities, feeling Nature does everything, I am non-doer (Akarta) , if you identify yourself with the action-less Self , no matter what work or how much of it is done, action is no action at all. This is inaction in action. By such a practice and feeling, action loses its binding nature.
A man may sit quietly. He may not do anything. But if he has the idea of agency or doership, or if he thinks that he is the doer, he is ever doing action, though he is sitting quietly. This is action in inaction. The restless mind will ever be doing actions even though one sits quietly. Actions of the mind are real actions. "Nor can anyone even for one moment remain really actionless, for helplessly is everyone driven to action by the qualities of Nature." (Chapter III. 5)
Inaction also can induce the feeling of egoism. The inactive man says, ‘I sit quietly; I do nothing’. Inaction, like action, is wrongly attributed to the Self.
He is the performer of all actions who knows this truth. He has attained the end of all actions, i.e., freedom or knowledge or perfection.
When a steamer moves, the trees on the shore which are motionless, appear to move in the opposite direction to a man who is in the steamer. Moving objects that are very far away appear to be stationary or motionless. Even so in the case of the Self, inaction is mistaken for action and action for inaction.
The Self is actionless ( Akarta or non-doer, Nishkriya or without work). The body and the senses perform action. The actions of the body and the senses are falsely and wrongly attributed by the ignorant to the actionless Self. Therefore the ignorant man thinks, ‘ I act’. He thinks that the Self is the doer or the agent of the action. This is a mistaken notion. This is ignorance.
Just as motion does not really belong to the trees on the shore which appear to move in the opposite direction to a man on board the ship, so also action does not really pertain to the Self.
This ignorance which is the cause of birth and death vanishes when you attain Self-realisation.