I feel that people who are clever enough to raise this question are also clearly clever enough to answer it for themselves. Anyway, operationally speaking the

I feel that people who are clever enough to raise this question are also clearly clever enough to answer it for themselves. Anyway, operationally speaking the difference is in how easily the matter in question can be digested by living things. If it's easy to digest it's food, if it can't be digested at all then it's worse than artificial: it's anti-life.