B.G 18.18

jñānaṃ jñeyaṃ parijñātā trividhā karmacodanā। karaṇaṃ karma karteti trividhaḥ karmasaṅgrahaḥ ॥18॥

Knowledge, the object of knowledge, and the knower constitute the threefold impulse to action. Correspondingly, instrument, action, and the doer form the threefold aggregate of causes of actions.

Gīta Bhāshya 18.18

The term 'karma saṅgrahaḥ' in the context means 'collection of causes of actions'.
The hypothesis that recommended injunctions and moral rules have no effect on sentient beings because of the non-agency, similar to inert insentient things, is refuted. A sentient being differs from an insentient because of its intentionality (apekṣya), which arises from knowledge, the object of knowledge and the knower. Even in inaction, the egoistic sense of doership, i.e. intentionality is involved. Even when one is not the doer, desires arise by the grace of God, instrumented, based on the stated causes (knowledge, the object of knowledge, and the knower) through the method, and the benevolent human goal is achieved through actions.

evaṃ tarhi na puruṣaṃ apekṣya vidhiḥ। akartṛtvāt ityata āha - jñānaṃ iti॥

Then, if it is postulated, that the rule does not dependent on a person due to non-agency, it is contradicted by the verse 'jñānaṃ', i.e. 'knowledge'.

trividhā karmacodanā। etat trividh mapekṣya karmavidhiḥ iti trividhā ucyate। kāraṇāni saṅkṣipyāha - karaṇaṃ iti॥

The impulse to action is threefold (viz knowledge, the object of knowledge, and the knower). Considering this threefold impulse, the procedure of how action come about is described as threefold (instrument, action, and the doer). The causes (five types stated earlier) are summarized here as 'karaṇaṃ' i.e. the instrument.

karma saṅgrahaḥ karmakāraṇasaṅgrahaḥ। adhiṣṭhānādi karaṇe eva antarbhūtaḥ। tathāhi ṛgvedakhileṣu -

The term 'karma saṅgrahaḥ' in the context means 'collection of causes of actions'. Earlier indicated 'adhiṣṭhāna' i.e. body and others, are indeed included in the term 'instrument'. Hence, it is stated in Rigvedakhila:

"jñānaṃ jñeyaṃ jñāninaṃ cāpyapekṣya vidhirutthitaḥ। karaṇaṃ caiva kartā ca karmakāraṇasaṅgrahaḥ॥"

"From 'knowledge, the knowable, and the knower' comes forth the intentionality governed by the methods and rules. The instrument and the doer are collectively the cause of actions."

iti।

- stated thus.

akartṛtve'pi vidhidvāra īśvaraprasādāt icchotpattayā ukta kāraṇaiḥ karmadvārā puruṣārtho bhavatīti। īśvarādhīnatve'pi vidhidvārā niyataḥ tenaiva। yadi ca icchādiḥ jāyate tarhi kāritameva īśvareṇa। phalaṃ ca niyatam। vastuto akartṛtve'pi abhimānikaṃ kartṛtvaṃ tasyaiva। svātantryaṃ ca jaḍamapekṣyeva iti na pravṛttividhi vaiyarthyām। sarvaṃ caitat anubhavoktapramāṇasiddhaṃ iti na pṛthak pramāṇamucyate ॥18॥

Even when one is not the doer, desires arise by the grace of God, instrumented, based on the stated causes (Knowledge, the object of knowledge, and the knower) through the method, and the benevolent human goal is achieved through actions. These depend on God alone, operated by Him through the governing methods. If desires arise, then they are indeed caused by God. The results are also obtained through governing principles. In reality, even in non-doership, the egoistic sense of doership, i.e. intentionality, is involved which comes under His governance. Indeed, independence (of the sentient agent) is significant in comparison to the insentient due to its intentionality, and thus the injunction (to act) is not futile. All this is established by experiential evidence, and thus separate evidence is not required.