Abstract

I attempt to define the concept of ‘living organism’. Intuitively, a living organism is a substantial entity with a capacity for certain relevant activities. But biology has discovered that living organisms have a particular compositional or microstructural nature. This nature includes carbon-based macromolecules and water molecules. I argue that such living organisms belong to a natural kind of compound physical object, viz., carbon-based living organism. My definition of a living organism encompasses both the intuitively relevant activities and the empirically discovered compositional nature. The definition is designed to deal with a variety of problem cases, e.g., viruses, proteinoid microspheres, sterile organisms, suspended animation cases, and living parts of organisms.