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.