When there is duty, that is another thing. But not whimsically. We cannot kill. Therefore Lord Jesus Christ ordered, "Thou shall not kill." This is the order. "Thou shall not kill." But we are violating the order. We are killing so many animals. So this is not good. On the plea that "Lord Christ sometimes took some fish somewhere; therefore we will have to maintain a big slaughterhouse," this is not very good logic.
So anyway, we have to act according to the superior order. And so far the spirit soul is concerned, that is the first lesson of spiritual knowledge. Unless you understand what is spirit... We are present here. The body is there and the spirit is there. Now we must analyze according to the direction given in authoritative books. That is very easy. Kṛṣṇa says that within this body there is the spirit soul. And we can experience that unless the spirit soul is there, the body does not change, and as soon as the spirit soul goes away, the body is a dead lump of matter. That's all. Very easy to understand. So we have to first understand this, then spiritual progress. If we remain like asses and dogs and cats, that "I am this body," there is no question of spiritual understanding. Therefore we are presenting Bhagavad-gītā As It Is. Read it and you will understand what is the difference between spirit and matter. In so many ways they have been described. Then if we understand that "I am not this body. I am spirit soul," then my duty will be assigned, that "I am spirit soul, ahaṁ brahmāsmi. So I am acting for the body only? The body is perishable." Antavanta ime dehāḥ. Everything is there. Antavat means perishable. Nityasyoktāḥ śarīriṇaḥ: "But the spirit soul is eternal." So I am working day and night so hard only for this body, how to eat, how to dress, how to have sex, how to defend. What I am doing for the spirit soul? That is knowledge. The spirit soul, I am the spirit soul, and because as spirit soul I am within this body, the body is working, moving, and I am simply taking care of the body. What care I am taking for myself, the spirit soul, who is going to change this body?