Once we agree that killing and harming living beings is a bad thing, there are still some ambiguous situations.
One question: is it ever good to kill? Here’s a Q&A from Ven. Dhammika on this difficult topic.
Question: But surely it is good to kill sometimes. To kill disease-spreading insects, for example, or someone who is going to kill you.
Answer: It might be good for you. But what about that thing or that person? They wish to live just as you do. When you decide to kill a disease-spreading insect, your intention is perhaps a mixture of self concern (good) and revulsion (bad). The act will benefit yourself (good) but obviously it will not benefit that creature (bad). So at times it may be necessary to kill but it is never wholly good.
(p.27, Good Question Good Answer by Ven. S. Dhammika, published Buddha Dhamma Mandala Society)
As Venerable Dhammika points out, some situations require that we weigh the multiple consequences of the action being contemplated. Killing disease-spreading insects might well be, on balance, a better course of action than leaving them to breed. It could benefit many sentient beings. We could first consider whether there is an alternative to mass killing, such as removing breeding places near human populations. Even if a mass wipe-out is deemed necessary, the actions should be taken with a clear picture of the compromise, consciously minimizing any hatred of the insects. Whenever we kill a living being, there is a negative consequence to our own mind. When we engage in intentional harm, it’s important to affirm the sadness in the act as well as the wholesomeness of the end result.
The question of killing another human, fortunately, comes up very rarely, unless one is a soldier on the battlefield. Even there, it’s no secret that to kill another human being is very difficult. There is internal resistance and revulsion, even from trained soldiers. Few military personnel completely recover from the damage done to their spirits if they are forced to kill in the line of duty. Doesn’t this confirm a deep knowledge that we oughtn’t to be doing it? Personally, I would rather be killed than kill anyone, because of the karmic consequences. I hope none of you ever has to make that choice. Part of the wisdom of harmlessness is to try to keep yourself out of situations that increase the likelihood that you’ll commit a seriously harmful act.
Another group of tough questions involves euthanasia and suicide. I’m afraid I don’t have a good answer for all situations. The Buddha taught that taking life, even one’s own, brings negative consequences beyond the act itself. But there are grey areas. Is is OK to starve oneself to death rather than endure end-stage cancer? Should you leave the room knowing your dying loved one intends to kill him or herself?
One answer I can give, supported by Sogyal Rimpoche, author of the Tibetan Book of Living and Dying, is that keeping someone alive simply because we can is not a good idea. If there is no chance of the dying person generating positive mindstates with which to die, then probably better to let nature take its course without interference.
It can be unpleasant to think of this precept on harmlessness because it brings up the reality of our own unavoidable end. Life is short. All we can do is do our best with the time we’ve got, and maybe gain some wisdom in the process.