Knowledge, the knowable and the knower form the threefold impulse to action; the organ, the action and the agent form the threefold basis of action.
In simple words
Krishna describes what drives action: "Three things push a person to act — knowledge, the object of knowledge, and the knower. And three things make up the act itself — the instrument, the action, and the agent."
Word-by-word meanings
ज्ञानम्knowledgeज्ञेयम्the knowableपरिज्ञाताthe knowerत्रिविधाthreefoldकर्मचोदनाimpulse to actionकरणम्the organकर्मthe actionकर्ताthe agentइतिthusत्रिविधःthreefoldकर्मसंग्रहःthe basis of action
Contemporary scholarly and practical interpretations for modern seekers.
Swami Sivananda
18.18 ज्ञानम् knowledge? ज्ञेयम् the knowable? परिज्ञाता the knower? त्रिविधा threefold? कर्मचोदना impulse to action? करणम् the organ? कर्म the action? कर्ता the agent? इति thus? त्रिविधः threefold? कर्मसंग्रहः the basis of action.Commentary Knowledge? the knower and the thing to be known? are together the seed of this world. This is known as the Triputi or the traid. It is the conjunction of these three that impels a man to threefold action? viz.? mental? verbal and physical. This triad is the driving force of all the activities of man. He rejoices at the sight of palatable sweetmeats and delicious fruits but is terrified at the sight of a cobra or tiger. The sight of pleasant or unpleasant objects affects him and he attempts either to possess the agreeable objects or to avoid the disagreeable ones.The Antahkarana (the inner instrument) consists of the mind? intellect? subconscious mind and egoism. The ear? the skin? the tongue? the nose and the eye are the five organs of knowledge. The individual soul? propelled by these five senses? is led into activity. He does actions with the help of the five organs of action? viz.? speech? hands? feet? genitals and anus.Jnanam Any knowledge knowledge in general knowledge of worldly objects? etc.Jneyam The object to be known objects in general.Parijnata The knower? the experiencer or the enjoyer? putting on the nature of the limiting adjuncts? a creature of ignorance.This triad forms the threefold impulse to all action? to action in general. The performance of an action in order to get a thing or to avoid an object is possible only when there is the conjunction of the three? viz.? knowledge? knowable and knower.Karanam The organ That by which something is done. The actions done by the five causes of action? viz.? the body? etc.? which are grouped under the three classes according to their respective seats? viz.? mind? speech and body? are all due to the interplay of the organ? etc.Karta The agent or the doer he who sets the organs in motion or action and puts on the nature of the limiting adjunct or vehicle in which he acts. All actions inhere in these three (the organ? the doer and the action itself) and they are? therefore? said to form the basis or the threefold constituents of action.As action? the various factors of action and the fruits are all made up of the Gunas? the Lord describes them in the following verses.
Swami Chinmayananda
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
In BG 18.18, the Lord Sri Krishna, having reasoned through the nature of action and described the five causes of action's performance, as well as pointing to the doer-less atman distinct from these, now expands upon this subject. He reveals the three impulses of action and the threefold instrument of action through which action becomes possible.
Every action is impelled by knowledge of its object. For the accomplishment of this knowledge, three elements are necessary: the knower, the known (the object of knowledge), and knowledge itself (the understanding gained through the act of knowing). The knower, the known, and knowledge—these three are called the triputi in the language of Vedanta. It is through the relationship of these three that knowledge of the object which prompts action arises.
The impulse to action may arise in three ways: (1) as a desire born in the mind of the knower, (2) from the allure of the object of knowledge, or (3) from the memory of previously experienced pleasure (known happiness). Beyond these three, there is no other cause that impels action.
After the impulse to action arises in the inner faculty, the accomplishment of that action requires the triputi of doer, instrument, and action—here called the threefold instrument of action. The living being, impelled by desire, enters the field of action with the sense of doership ("I am the doer"). Here the living being is called the doer. The fruit or goal which this doer-being desires is indicated here by the word action. Here action means the fruit itself.
To obtain the fruit (action), the doer-being must perform activity. The means of this activity are called instruments, which include the senses of perception, the senses of action, and the mind and intellect. Thus, the doer, the action, and the instrument—these constitute the triputi of action, or the threefold instrument of action.
Without any one of these three, action cannot be accomplished.
The entire universe is the work of prakriti, which is threefold in its gunas. Therefore, in knowledge, action, and the doer, threefold distinctions arise due to the three gunas, which shall now be described. The Lord speaks: