Is killing vermin and insects justifiable?

Killing is never justifiable.

He cares not to step on an ant while walking, but did once while not paying attention. He walked on and he has learnt.

She likes the rose and plucks it and get stung by the thorns. She doesn't afterward try to get a tool to cut it to prevent another cut or step on it as retaliation. She looks, instead.

"such as mosquitos in places where malaria is common"

would be the same as someone who cusses at you for no reason, makes you angry, a cause arises in the sense, which in turns justifies your retaliation ad urges you to do it.

In the arising of cause in the sense, it draws a line for you "right" and "wrong", "good" or "bad", "kind" and "evil", put your feeling in one of them, urges you to counter the opposite of the other.

In Buddhism one of the main teaching is that any action as repercussions. Generally people do not like getting wounded, loosing a limb or body parts, dyeing, etc. When you do bad Karma the results you reap are similarly horrible as your action. So what you do to the insect will likely befall you in some point of your existence in Samsara.

Since this action in not to ones own benefit or the benefit or other hence is it unjustifiable. What is justifiable is what beneficial to ones self and others.

NB: In Buddhism the law of Karma is not absolute, but balance of probability interacting with the other Karma and Niyamas.

Also see the following which analyse the results of Karma. Generally what is not conducive to oneself or the others is not justifiable:

• Cula Kamma Vibhanga
• Brahmavihara Subha
• Ananda Subha
• Maha Kamma Vibhanga

As a practicing Buddhist, I would say, no, it is not. Part of the problem is that great thought has been put into methods of killing, but relatively little thought has been put into alternatives to killing. When I find mice in my house, I drive them to the park.

I have heard that there is some investigation into breeding mosquitoes that pass on a gene that makes their progeny sterile, or something like that. Thus killing can be avoided in that situation.

I stopped killing mosquitoes long time ago and started using nets and mosquito repellent lotion. You really don't have to kill them.

First rule (of layperson) is actually includes intentional killing of any animals down to even insects. See for reference http://www.accesstoinsight.org/lib/authors/bodhi/wheel282.html#prec2

"I undertake the training rule to abstain from taking life." Here the word pana, meaning that which breathes, denotes any living being that has breath and consciousness. It includes animals and insects as well as men, but does not include plants as they have only life but not breath or consciousness. The word "living being" is a conventional term, an expression of common usage, signifying in the strict philosophical sense the life faculty (jivitindriya).

But you will not be expunged from being buddhist if you violate that, you just stain karma, accumulate demerit, and lose protection.

I feel like sometimes the "plain", most obvious meaning of the rule (e.g. don't kill people) is taken to extremes (e.g. killing mosquitoes that spread diseases which kill you, killing a bear which is eating you), and the very intuitive repulsion the mind feels regarding the extreme is used to sow doubt in the rule itself.

I don't think the Buddha taught by going to extremes like this. How about start off by not killing people, for any reason. This, at least, is pretty straightforward, how the hate and lack of compassion required for killing people is damaging to you.

Next, examine the ways in which you'll sometimes casually kill insects and set it within the context of kamma and rebirth. Does it seem unskillful? If it does, then abandon it. Next, examine how you'd feel if something were trying to kill you. Do these actions of your mind reacting against the assailant seem unskillful? If they do, then abandon it.

Think of it like taking your mind to progressively more subtle forms of self-examination to abandon more and more forms of unskillful behavior.

The way of thinking in the original post is more like taking the prohibition on killing to an extreme and then allowing the mind's repulsion against the extreme case to take over and turn you against the precept.

But the mind that hasn't gone beyond suffering is the problem. You have to be careful how you let it make decisions about these things.

There are instances where the Buddha says a question should be answered with a yes/no response and others where the answer should be qualified by re-defining the question. http://obo.genaud.net/dhamma-vinaya/ati/an/04_fours/an04.042.than.ati.htm

First the categorical answer, then the qualified, third, the type to be counter-questioned, and fourth, the one to be set aside. Any monk who knows which is which, in line with the Dhamma, is said to be skilled in the four types of questions: hard to overcome, hard to beat, profound, hard to defeat. He knows what's worthwhile and what's not, proficient in (recognizing) both, he rejects the worthless, grasps the worthwhile. He's called one who has broken through to what's worthwhile, prudent, wise.

It's not justifiable even if the killing is for self or others protection.

If killing of an animal fulfills below five conditions it will give bad results (akusla karma vipaka)

1. There should be a living being
2. Knowing that its a living being
3. Intention of killing
4. Act to kill
5. Animal is killed by the act

Note: Even If someone kills an animal which is suffering from unbearable pain (like with an injury), with the intention of releasing it from the pain. It will give Akusala Karma vipaka.

The five precepts are an absolute entry-level teaching that is designed to help the practitioner master basic discipline of self-control and self-reflection.

Abstaining from killing, stealing etc. implies basic ability to watch one's mind for harmful thoughts and emotions, and to prevent them from getting acted out.

In light of the above, the no-killing rule should not be understood literally, as an absolute law, but as a guideline for training the mind. It is not acceptable to hurt or harm any creature (big or small) out of anger, out of competitiveness, or out of ignorance. This is what this rule is about.

In order to understand this issue, we have to understand morality according to Buddhism. In Theravada Buddhism, morality is completely based on the effect that an act has on the mind of the actor. Hence, eating meat need not be karmically negative, yet killing Hitler to "save" others from suffering need be, since it requires defilement to take the life of another.

It is not considered immoral to do something just because it has negative consequences for others, nor does a positive effect for others constitute a sufficient condition for morality.

The reason for all this is that Buddhist morality is defined by its potential to lead to focus/concentration and eventually wisdom. One eats meat, knowing that the act is harmless, and so one's mind remains calm and the nourishment supports meditation practice.

The reasons behind killing our less evolved brothers and sisters - insects, spiders, foxes, etc., are inconsequential. Even if killing a single mosquito would end all cases of malaria in the world for ever, the (Theravada) Buddhist philosophy would be to abstain from killing the mosquito. Acting to prevent suffering can actually considered to be an unwholesome act, since it generally requires aversion to said suffering. In (Theravada) Buddhism, we act to prevent unwholesomeness, not suffering, since suffering does not lead to suffering, but unwholesomeness always leads to suffering.