The buck so often stops, when we moralize about our treatment of animals, with the word 'sentient'. Usually, that we should care for one kind of animal because it is sentient - say, a dog; and not so much for another because it is not sentient - say, a fish or a bug. But what is 'sentient'? Well, it depends who you ask - or read. The definition is as elusive as the meaning of 'consciousness' itself. For one author its is an 'awareness of sensory input', and for the next it might be 'consciousness of sensory input and the self'. It is all so semantic, the whole lot of it, that the word does nothing to inform the philosopher within us. The problem with our vague definition of sentience is that it fails animals. This is because they cannot rely on any human argument to save them from suffering imposed by people, as none of our arguments to each other make any sense. Any attempt to draw a line in the sand around animal cruelty on the basis of sentience is therefore doomed to fail: 'Sentient you say? Then are you also saying that I should not step on an ant or even prune my jasmine creeper?' When there comes a real breakthrough in human understanding of consciousness and 'being', and a concomitant new definition of sentience, only then will we be able to make moral arguments about animal suffering. Until then, I would think we need to be guided by our hearts and stomachs more so than our minds. Does it appear to be uncomfortable or painful to the creature? Common sense, common decency and a normal instinct for compassion are all that are really required to inform a decision as to whether or not an animal may be harmed, as with a human. That line will be different for different peoples and people. But we should not cop out of personal responsibility for inflicting pain on anything on the ground that 'it is not sentient'.