Heh.... this is an issue that annoys my partner somewhat. When I say 'annoy', it is not as if she gets angry with me. She has very sensitive skin and is squirmish around some insects and bugs, so she clicks her tongue at me whenever I refuse to swat at them. But she understands and respects my reasons for not doing so, I must say.
Why do I refrain from killing mosquitoes, bugs, etc? I must say that my decision is not really based on a careful or thorough consideration of some of the very good points raised in this thread so far: issues about what qualifies as a sentient being, what qualifies as consciousness, the dynamics of kamma and rebirth, etc. To be sure, these issues are worth considering and thinking them through can help us get a better understanding of the Dhamma. However, if you have been around discussion forums long enough (and really you don't have to be at it for very long), I think you'll agree with me that there is no easy way to reach a consensus about such things. Debates about these issues then to go on and on, and in the process, they can sometimes generate feelings of annoyance and irritation amongst the participants, producing feelings of unwholesomeness. So this is partly one reason why, though I find these issues interesting, I do not usually dwell too much on them.
The main reason I choose to refrain from killing mosquitoes, bugs, etc, is NOT because I have figured out the answers to such questions. Rather, it is because each time I catch my urge to react blindly and stop myself from doing it, I EMBODY and ENACT my commitment to the Dhamma, to the precepts in particular. In that very brief moment when I choose to remain calm and equanimous, I LIVE the Dhamma; the Dhamma--and all the talk about non-violence, kindness, kamma, etc--become a living event rather than just concepts and propositions
. In that moment, debates about sentient beings/consciousness/kamma/rebirth become somewhat less urgent in comparison to how I choose to act in THAT very moment: whether I want to embody
wholesomeness or not.
Again, I must say that thinking through these issues can help us develop Right View. But in those moments when I'm confronting an annoying mosquito buzzing around my ear, my decision is oriented by Right Effort (which is about honouring my commitment to wholesomeness, to the precepts) more than anything else. Questions about the 'rightness' or wrongness' or the 'truthfulness' and 'falseness' of statements about consciousness, sentience, etc, take a back seat to whether I choose to EMBODY wholesomeness or not, so that I may LIVE the Dhamma rather than merely engage with it as a set of rules, statements, and propositions.
Now, if only my partner would stop giving me grief for being blasé about insects hanging out in the bathroom.... but I love her for it, nonetheless.