The third aspect of Right Intention on the Buddha’s eight-fold path is the intention of harmlessness. The first two are intention of renunciation and of good will.
The intention of harmlessness is thought guided by compassion (karuna), aroused in opposition to cruel, aggressive, and violent thoughts. Compassion supplies the complement to loving-kindness. Whereas loving-kindness has the characteristic of wishing for the happiness and welfare of others, compassion has the characteristic of wishing that others be free from suffering, a wish to be extended without limits to all living beings. Like metta, compassion arises by entering into the subjectivity of others, by sharing their interiority in a deep and total way. It springs up by considering that all beings, like ourselves, wish to be free from suffering, yet despite their wishes continue to be harassed by pain, fear, sorrow, and other forms of dukkha.
Bhikkhu Bodhi, from http://www.accesstoinsight.org/lib/authors/bodhi/waytoend.html#ch3
In practice, the intention of harmlessness is compassion for other living beings, a wish that they not suffer. We recognize that people are fragile and sensitive, even when they appear not to be. We try to put ourselves in others’ shoes, to step out of our own views and make the effort to imagine what other beings might be feeling, what vulnerabilities they may have.
In this, as in other activities, slowing down can be a big help. As Andrew Olendzki has said, “We don’t have free will; we have ‘free won’t’.” This is what I take him to mean: It is impossible to insulate ourselves from our histories and current stimuli (for good or ill), but we can choose to NOT act on an impulse that arises. For me this connects with the idea: “First, do no harm”. When we are unsure about what to do, doing nothing (for a time) is often the best path to take.
Intentions are the link between our views and our behavior. Before any word or action, there is an intention, which we may or may not be aware of. Because our own intentions are sometimes hidden from us, we can only guard against any harmful intention (and appreciate our intentions of harmlessness) through mindfulness that is as continuous as possible. Sometimes it’s only after we act that we see what our intention was. Sometimes it becomes clear in the middle of an act, and sometimes we are alert to our intentions before we act. With practice, we can choose to follow our wholesome intentions and set aside our unwholesome ones.