Science

What makes an object living? Scientists have a number of qualities that an object needs to have to be considered living: Self-replication etc. What qualities do philosophers associate with living objects?

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Philosophers might put the question like this: what constitutes being a living thing? And we might hope for a non-circular definition that spells out exactly what it takes to be a living thing.

Among the strategies for answering this sort of question, a common one is conceptual analysis. This strategy is applicable when we think competence with the concept in question (in this case, the concept of a living thing) gives us a kind of seat-of-the-pants knowledge of what it is for the concept to apply to a thing, so that what's left is to turn our commonsense expertise with the concept into a careful definition. We propose a definition, and then test it by trying to imagine an example of a sort of thing that meets the proposed definition but where the concept doesn't really apply (according to our commonsense expertise), or vice versa. Suppose we try that with the concept of a bachelor. Someone proposes the definition unmarried male human. But a newborn boy is surely not a bachelor. So we refine the definition: unmarried adult male human. But this would rule out Martian bachleors as a matter of definition, and that seems wrong. Okay: unmarried adult male person (where "person" covers not only humans but appropriately personable other species). But is the Pope a bachelor? You get the idea. Maybe the process has a quick, successful conclusion, maybe not. (Some philosophers have claimed and/or argued that it will never have a successful conclusion because concepts never really have definitions in terms of other concepts, let alone ones that we can discover by this kind of head-scratching.)

The philosopher Hilary Putnam famously argued that with respect to certain concepts he called natural kind concepts, conceptual analysis is bound to fail, and not because there isn't a correct definition of such a concept, but because the definition can't be extracted from ordinary competence with the concept. Consider the concept of a lemon. A correct definition of that concept would spell out what distinguishes lemons from anything else there might be, including fake lemons that would fool you and me. Perhaps the correct definition would have to identify the species of the lemon tree using genetic or other biological taxonomic concepts. If so, then what it takes to determine the correct definition is empirical research into the actual features of lemons (the samples that prompted the concept lemon in the first place), rather than armchair conceptual analysis. (But notice that it's armchair thinking that has established this!)

So an interesting question is whether one of these two strategies is appropriate for the concept living thing, and if so, which one. Is a capacity for reproduction essential to being a living thing? If we're doing conceptual analysis, then we might well conclude not, for it is easy to imagine a laboratory-created plant-like organism which grows, photosynthesizes and so on but which has no capacity for generating copies of itself, and surely we'd want to say that such a thing was alive (right?). But if we take "living thing" to be a natural kind term, then we might point to empirical facts about what actual living things have in common---perhaps certain specific organic processes that underlie their capacities to nourish and reproduce. Then, lab-created growy things, however life-like, could well technically not count as being living things (just as a fake lemon is not really a lemon, and fool's gold not gold).

Does one of those strategies seem more promising than the other? Is what it is to be a living thing something that ordinary folk intuitively already know, or is it a matter for scientific, rather than armchair, discovery? Can this question be settled from the armchair? Does the assumption that it has an answer impute too much precision to our ordinary concepts?

Don't you hate it when philosophers end their answers with questions?

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