Buddhism is less about following rules and more about abandoning self-serving narratives. The Precept, “I resolve not to kill but to cherish all life”, must be understood on three levels – fundamentally as an exercise in mindfulness; flexibly as a guide to ethical living; ultimately as a meditation on selfless interdependence.
WHAT DOES “I RESOLVE NOT TO KILL BUT TO CHERISH ALL LIFE” TRULY MEAN?
Buddhist precepts can be understood on three levels.
“I resolve not to kill but to cherish all life” can be understood literally as a firm determination never to harm any sentient being, ever. Engaging with the precept at this basic level is a valuable training in mindfulness, as it requires restraint and vigilance to avoid breaking one’s vow. Maintaining such a fundamentalist attitude isn’t conducive to peace of mind in the long run, however, and unlike the Buddha one may even develop an attitude of self-righteous intolerance towards others who fail to do likewise.
When I first took on the training rule of refraining from killing I adopted a ‘live and let live’ attitude to household ‘pests’ and strived to leave them be instead of swatting them, stomping them, or poisoning them. I remember one summer in particular when our house was repeatedly invaded en masse by the ants that were nesting under the doorstep. Destroying them all with pesticide seemed the most obvious way to rid myself of the problem and I was sorely tempted. With my fundamentalist understanding of the precept, however, I would instead grit my teeth and use a vacuum cleaner to suck up the offending creatures and tip them all back into the garden afterwards. I felt virtuous for a while but the ants kept coming back. So I opted for a middle way solution, which was to spray a little pesticide underneath the front door now and again to deter the ants from entering the house. The strategy still seems to be working – the ants are staying in the garden and I simply acknowledge any guilt I may occasionally feel about supporting the poisons industry just a little bit.
The above anecdote illustrates how compassion for oneself and for others requires a more flexible engagement with the precepts. A resolve not to kill but to cherish all life takes place within a context that never remains the same from one moment to the next. One might be asked to assist a suicide or an abortion, for example, and a point blank refusal to help may not be the most compassionate response. I’m not of course saying that precepts are disposable or even that breaking them is sometimes justifiable. But in a given set of circumstances, choosing to break a precept instead of upholding it regardless may be the lesser extreme – as in one of the Jataka Tales:
The captain, a bodhisattva himself, saw the man’s murderous
intention and realized this crime would result in eons of torment for
the murderer. In his compassion, the captain was willing to take
hellish torment upon himself by killing the man to prevent karmic
suffering that would be infinity greater than the suffering of the
murdered victims. The captain’s compassion was impartial; his
motivation was utterly selfless. 
A flexible attitude without full awareness of one’s values and motivations can easily render a precept meaningless or hypocritical. In my opinion, ‘mercy killing’ is a dubious practice that’s very difficult to justify, however I can see that it might be the more wholesome choice in particular cases even though I cannot really know the minds of those involved.
The experience of ‘self’ and ‘other’ is illusory, conditioned by innumerable sensory contacts; a matter of cause and effect with no discernible beginning or end. Conventionally one speaks of ‘doers’ and ‘deeds’, but closer examination reveals only a process of ceaseless change. Ultimately one sees only amalgams of mental and material phenomena in constant flux; stream-like flows arising from an unfolding of past events; imbued with a potential to influence the unfolding of future events; requiring nurturing and nourishment in order to become actualised. This ultimate perspective doesn’t justify an ‘anything goes’ policy just because there’s ‘no one actually suffering’. (There will be unpleasant consequences real enough for anyone who adopts such an ignorant attitude!) The ultimate perspective is, however, an important and useful contemplation when confronted with life’s seemingly impossible conundrums.
Understanding that ultimately there’s no abiding self separate from the universe, one’s resolve not to kill but to cherish all life can evolve from a desperate clinging to a scriptural training rule into a firm determination to limit one’s capacity for harm. One strives to remain aware of the present moment reality; to abandon all self-centred delusions (such as pride, greed, and hatred); to cultivate a mind of universal compassion.
Within Buddhism the term ‘Sentient Being’ often excludes life forms such as plants and bacteria, as they are considered not to possess a mind that’s capable of interpreting sensory stimuli.  But if sentience is ‘feeling or sensation’  or the most primitive and simple form of cognition… the state of being sentient… being aware of stimuli without interpreting it”  then I think that along with all the usual suspects we also have to consider plants, bacterial life forms, and other responsive invertebrates, as sentient. To dismiss them as ‘non-sentient’ or ‘without a mind’ may be doctrinally correct but it’s also practically convenient and a powerful self-serving justification for killing them, in my opinion.
We cannot truly know minds other than our own. We can infer from our own experiences how others may or may not suffer, but we shouldn’t concretise our experiences nor should we believe our assumptions about others to be infallible. If we truly understand interdependence and our place within a web of sentient predators and prey we will stress less over the rights and wrongs of meat-eating versus vegetarianism or veganism, for example, and strive more to reduce our demands on the universe by living simply, being content with little, eating only when hungry and refraining from justifying our lifestyle choices with dubious appeals to morality, science, or scripture. Yes, buying animal products encourages others to profit by hunting or imprisoning and eventually slaughtering fish, fowl, cattle and game. Yet buying fruit and vegetables also induces crop growers to profit by destroying natural habitats and killing ‘pests’ with ploughs, bullets, and poisons, and is no less heinous. Neither choice can be justified without resorting to psychological projection and speciesism.
The Buddha taught that to be born is to suffer. The Path to Nibbana (freedom from the sorrows of birth, ageing, sickness and death) requires gradual abandonment of all views, all desires and expectations. He implored us to face samsara square on; to retain a sense of gratitude as we feel the pain of existence; to stop clinging to narratives that ignore the whole truth but give us instead a false sense of security and moral superiority; to acknowledge our failings and the failings of others with compassion, not condemnation.
Impermanence (anicca), suffering (dukkha), not-self (annatta) is the Buddha’s truth and it’s unlikely therefore that he regarded any rule or precept as appropriate every time in every changing circumstance. As one of my teachers might say, there’s little point in resolving not to kill but to cherish all life if one is never tempted! Moreover, I would also add there’s little point in doing so without some willingness to make lifestyle changes that will reduce one’s personal consumption of precious resources and offset some of the unintentional harm that one inevitably does to the biosphere. One might do better working with an easier precept if that’s the case. The challenge of not killing but cherishing all life can be resumed when one is ready to take it seriously.
To conclude: “I resolve not to kill but to cherish all life” must be understood on three levels – fundamentally as an exercise in mindfulness; flexibly as a guide to ethical living; ultimately as a meditation on selfless interdependence.
Buddhism is less about following rules and more about abandoning self-serving narratives. When aiming to walk The Path one must strive always to apply mindfulness. Keep looking, keep noting the situational changes, and keep updating the reality map. Get reality checks from noble friends and teachers. Keep on choosing the most appropriate navigational strategies. Discard whatever is known through personal experience to be unwholesome or ineffective.
 Chagdud Tulku – quoted in ‘Violence & War’, Khandro.Net.
 ‘”Sentient beings” refer to all living beings that have “sentience”, or, “awareness” / “mind” / “feelings”, those which can feel pain and pleasure. Human beings, animals, insects, and others not seen by the ordinary eye (“heavenly beings”, ghosts, and beings in hell) are sentient beings. Plants are not sentient beings (despite what some new findings seem to suggest, there is no real evidence that plants have sentience.) All sentient beings may become enlightened (and therefore, become Buddhas). Killing a sentience being cause various degrees of pain and suffering, and therefore is bad karma.’ – ‘Buddhism Q&A: What are sentient beings? Why do we refer to “sentient beings” instead of “human beings”?’, Chung Tai Zen Center of Sunnyvale.
 ‘Definition of Sentience’, Merriam Webster.
 ‘What is Sentience’ by Pam MS, NCSP, Psychology Dictionary.
‘Settling Into The Heart Of The Buddha’ by Roshi Wendy Egyoku Nakao, Zen Centre of Los Angeles.
‘Precepts And Meditation’ by Denis Walez, Koan.
‘On Interpreting The Teachings’ by Denis Walez, Koan.
‘Misperception: S/he’s Making Me Suffer’ by Paul L, Trusting In Buddha.