You: That is a strong argument, but before you can convince me of it you will have to explain exactly what you mean when you use the word "life?"
Aaron: Surely that is a trivial question. You and I both know exactly what life is. You are avoiding the question.
You: Not at all. If you cannot define life then you cannot tell what things are living and what things are not. A column of smoke or a stream of water, for example, might seem to be alive if we judge by the apparent intelligence of its movements. And if by life you mean a "life force" or some such metaphysical concept, then I will have to...
Aaron: Yes, yes, yes. I see where you're going and I certainly won't let you trap me so easily. I would say that living creatures are those which move, grow and reproduce, and that life is whatever force allows them to do these things.