Many readers take it this way. In chapter 11 the Lord tells Arjuna that these warriors are already slain and that he is to be merely an instrument. So the outcome is fixed and Arjuna is a tool, and his will, and ours, counts for nothing. The worry is serious, and the verses should answer it.
The answer is that what is fixed is the work of Time. Arjuna's choice is not counted in it. The Lord says "arise" to him, and at the end he says: reflect fully and then do as you wish. To be an instrument is to give up the claim on the fruit and the pride of being the only doer. It is not to give up choosing.
Why people read it this way
The reasons are in the verses. The Lord says he is Time grown vast, and that even without Arjuna these warriors will not remain (Gita 11.32). Then: they are already slain by me, be merely an instrument (Gita 11.33).
मयैवैते निहताः पूर्वमेव निमित्तमात्रं भव सव्यसाचिन् ॥ ११.३३ ॥
Therefore arise and attain glory. Conquer your enemies and enjoy a prosperous kingdom. By Me alone they have already been slain; be merely an instrument, O Savyasachi.
Chapter 18 has harder words. If, filled with ego, you think "I will not fight", your resolve is false, for your nature will drive you to it (Gita 18.59). What you do not wish to do through delusion you will do helplessly (Gita 18.60). And the Lord dwells in the hearts of all beings and turns them by his power as if they were mounted on a machine (Gita 18.61).
These verses are there, and it would be wrong to hide them. What matters is what stands around them.
What does the Lord fix, and what does he ask of Arjuna?
What is fixed in chapter 11 is the work of Time. "Even without you" (Gita 11.32) tells Arjuna that his fighting or not fighting will not change what happens to these warriors. It is said to a man full of fear and guilt, and it lightens his load.
But the verse begins with "arise" (Gita 11.33). A command or a call goes to someone who can hear it and might not. Then comes "win glory". And Arjuna's answer is not a tool's answer. He trembles, folds his hands and speaks again in a faltering voice (Gita 11.35). A living man is replying.
So what does "instrument" ask? What the Gita has said before: you have a right to action alone, never to its fruits (Gita 2.47). And the mind deluded by ego thinks "I am the doer", while actions are done by the qualities of nature (Gita 3.27). To be an instrument is to act without believing that the whole plan and the whole result rest on you. The fuller account is in Merely an Instrument.
What comes right after the hardest verses?
This is the key point. After the hard verses on nature and the machine the Lord says: take refuge in him with your whole being (Gita 18.62). Taking refuge is an invitation, not a push. And then:
विमृश्यैतदशेषेण यथेच्छसि तथा कुरु ॥ १८.६३ ॥
Thus I have declared to you knowledge more secret than the secret. Reflect on this fully, and then do as you wish.
"I have told you this knowledge, more secret than any secret. Reflect on it fully, and then do as you wish." The same Lord who says "you will do it helplessly" says a few verses later, "do as you wish". So the first has to be read with the second. The helplessness is that of a person who acts through delusion against what he really wants (Gita 18.60). When delusion goes, that helplessness goes too.
And at the end comes Arjuna's own sentence:
नष्टो मोहः स्मृतिर्लब्धा त्वत्प्रसादान्मयाच्युत ।
स्थितोऽस्मि गतसन्देहः करिष्ये वचनं तव ॥ १८.७३ ॥
Arjuna said: My delusion is destroyed, and I have regained my memory by Your grace, O Achyuta. I stand firm, with my doubts dispelled. I shall act according to Your word.
Arjuna says his delusion is destroyed, he has regained his memory, he stands without doubt and he will act on the Lord's word (Gita 18.73). "I will act" is his own word, said after reflection. He thanks the Lord's grace, but the one speaking is Arjuna.
Where does the Gita keep human effort?
Five causes are given for the success of any action: the seat, the doer, the instruments, the various efforts and destiny (Gita 18.14). The same five stand behind every act, right or wrong (Gita 18.15). The doer is one of them. The Gita does not rub him out. It only says that he is not the sole cause.
The Lord also says: lift yourself by your own self, and do not let yourself sink (Gita 6.5). That can only be said to someone who has something in his own hands. The same goes for the teaching not to come under the sway of attraction and aversion (Gita 3.34), which has meaning only if coming under it or not is partly up to us.
The misreading and what the verses say
| The misreading says | The verses say |
|---|---|
| The outcome is fixed, so there is nothing to choose | What is fixed is what Time will do (11.32); Arjuna is told "arise" (11.33) |
| An instrument is a tool with no will | An instrument has no claim on the fruit and no pride of sole doership (2.47, 3.27) |
| "Your nature will drive you" means there is no alternative | It is about a "no" born of ego and delusion (18.59-60); not coming under attraction and aversion is taught alongside (3.34) |
| The Lord turns all beings on a machine, so nobody is responsible | The next verses invite refuge and then say "do as you wish" (18.62-63) |
| Arjuna simply obeyed | After reflection Arjuna said in his own words "I will act" (18.73) |
The better reading
In "be merely an instrument" the outcome is with Time and the action is in Arjuna's own hands. The Lord asks him to rise and in the end leaves the choice with him. To be an instrument is not to refuse choice. It is to put down the weight of the fruit and the pride of "I alone am the doer" while choosing.
A caution against misusing the word
No one can excuse a wrong act by saying "I was only an instrument". In the Gita the one who acts for the Lord is without enmity to all beings (Gita 11.55), and the doer is counted among the causes of every act (Gita 18.15). The instrument's attitude lightens the burden. It does not remove responsibility.
Going deeper
For the whole passage on being an instrument, see Merely an Instrument. The Lord's last words are in The Final Counsel, and Arjuna's own answer is in Delusion Gone: I Will Act. The Scholarly reading of this question takes up the hard verses, the objections and the readers' streams in more depth.