Sentience

At some point as we descend the scale of complexity, we probably reach a place where the physiological mechanism is no longer adequate to support consciousness, and animals become like plants, capable of reflexive responses to stimuli, but not sentient. Precisely where this line between sentient and insentient beings should be drawn, I di not know. Worms and insects are certainly above it. Microorganisms are probably below it. But wherever scientific investigation ultimately places it, the line is certainly far lower than most of us have been willing to consider.

---The Great Compassion: Buddhism and Animal Rights, by Norm Phelps---