"nutrient and energy source" is an interesting perspective: we certainly can't live off radiation (or heat, or electricity, or whatever one might consider as di

"nutrient and energy source" is an interesting perspective: we certainly can't live off radiation (or heat, or electricity, or whatever one might consider as direct energy input) plus all the atoms contained in a lifetime worth of food arranged in simple monogamous molecules. We are no less dependent on other organisms arranging atoms into molecules our bodies can use as fuel and building blocks than a virus is dependent on a host cell for reproduction. I suppose that we can't really want a definition of life that excludes everything that isn't a plant?