Śyāmasundara: He says that duty is one's individual obligation to obey the categorical imperative by choosing the morally right action. In other words, duty means it is my duty to choose the morally right action, free from emotion.
Prabhupāda: Therefore, as soon as you say duty, duty should be prescribed by some higher authority. In that sense, this system is very scientific: brāhmaṇa, kṣatriya, vaiśya, śūdra. It is very scientific. For brāhmaṇa, these are the duties; a kṣatriya, these are the duties. Every duty may appear different, but because it is a command of the Supreme, by discharging these duties on different platform, he is serving the Supreme. If Kṛṣṇa says, "All right, I see you are a brāhmaṇa. Your duties are like this," "I see you are a kṣatriya. Your duties are like this," "I see you are a vaiśya. Your duties are like this..." But Kṛṣṇa says cātur-varṇyaṁ mayā sṛṣṭam (BG 4.13). I have divided, so Kṛṣṇa gives duty, that "Your duty is this, your duty is this, and your duty is this." And if he faithfully serves the duty, that means he is serving Kṛṣṇa. The duties may appear different, but because he is serving Kṛṣṇa, he is going to perfection. Just like in our institution, I am the head man, so I may say, "You paint. You preach. You type. You do this." So the duties may be different, but by discharging duty, you are serving me; therefore you are perfect. Similarly, duties are given by the Supreme. Because I see that you are a śūdra, you cannot discharge the duties of a brāhmaṇa. That is not possible. So you do your duty like this. So superficially it may seem that a śūdra's duty is inferior to the brāhmaṇa's duty, but if the śūdra is performing his duty in accordance to the order of the Supreme, then he is also serving. The service is the main point. The same example of our body, that the duty of eyes, seeing, it is different from the duty of the legs, walking. But walking and seeing, both of them are being utilized for the whole body; therefore all of them are useful. So there cannot be any fixed-up duty, neither is everyone able to follow the same principles. Therefore this varṇāśrama-dharma is very scientific. That is to be understood.
Śyāmasundara: So ideally it is the moral obligation of everyone to obey the moral command, but...
Prabhupāda: Not moral command—the supreme command. What is moral for you, it may be immoral for others. One man's food is another man's poison. So therefore Kṛṣṇa says to Yudhiṣṭhira, "Go and tell lies." That is moral. Kṛṣṇa says to Arjuna, "What is this nonsense? You fight. Kill them." That is moral. So moral means to obey Kṛṣṇa's order, God's order. That is morality. You cannot create morality. You are imperfect. Your senses are imperfect. You do not know what is actually moral. Therefore we should implicitly, blindly follow the orders of Kṛṣṇa or His representative. That is moral.
Śyāmasundara: So the real categorical imperative is to obey the Supreme.
Prabhupāda: That is right. That is moral. Other things, all immoral.
Śyāmasundara: He says that we must follow our duty—not mechanically, but out of respect for it.
Prabhupāda: Yes. Suppose if I say that "You do this," just like Kṛṣṇa says that "You go and say Droṇācārya." So unless he has got implicit faith... Yudhiṣṭhira was lacking that implicit faith. Therefore he said, "How can I say such lies?" But Arjuna is better than Yudhiṣṭhira. He thought that "Although I am thinking it is very moral not to kill my relatives, but Kṛṣṇa likes it, I must do it." That's all.
Śyāmasundara: He says that ethics or morality should be institutionalized, regardless of the individual circumstances.
Prabhupāda: He comes to the circumstances. Therefore the morality should be according to the circumstances.
Śyāmasundara: He says the opposite: regardless of individual circumstances, everyone should follow the moral imperative. But we say that circumstances determine how one follows.
Prabhupāda: Then suppose the (indistinct) state, "Thou shalt not kill." So why killing is going on?
Śyāmasundara: In wars.
Prabhupāda: In any circumstances. It is not that killing is stopped, although the state is meant for prohibiting killing. But there is still in the slaughterhouse killing is going on, in war killing is going on, and so many other places killing is going on.