Phil 101: What is Life?

Feldman is seeking an analysis of the notions of life and death. To be successful, he says, an analysis should not have any clear counterexample—that is, there should not be any intuitively clear cases that it classifies wrongly. (If there are controversial or hard cases that it classes one way rather than the other, that may be OK—if the analysis seems otherwise to be good enough.) To be successful, an analysis should also avoid relying on terms that are obscure or circular.

He stresses the difference between an analysis or definition of a notion like “death” and a criterion, or easily recognized test or indication, of death. Tests and criteria don’t tell us what death is. They only help us figure out when death is present or absent. Moreover, their success is measured by their practical usefulness. An analysis of death, on the other hand, isn’t directly supposed to solve any practical problem. It’s successful when it helps us better understand what death is.

For the time being, Feldman supposes we can understand “death” like this:

Later in the course we’ll see some complications with this, but let’s accept it for now. This shifts our focus to what it is for something to “be alive” at a time.

In Chapter 2, Feldman discusses a strategy for defining life that dates back to Aristotle. Aristotle thought that life could be explained in terms of certain capacities or functions:

• nutrition: the capacity to get and use food
• reproduction
• the ability to sense or perceive things
• the ability to move oneself
• the ability to think

Feldman doubts whether this list of capacities can be combined into a satisfactory definition of life. How should the combination go? To be alive, does one have to possess all the capacities? That seems to leave out some clear cases of life. Is it enough to just possess any one of the capacities? That would wrongly count mechanical toys as living, since they have the ability to move themselves. Is there some one special capacity, perhaps nutrition, such that we can define living in terms of having it? Feldman objects that some moths intuitively still count as living for a while, even after they’ve lost any capacity to get and use food. Should we count things as living when they’ve ever in the past had the capacity of nutrition? That doesn’t work either. As Feldman points out, all corpses used to have the capacity to get and use food, but it would be wrong to count them as (now) living. So it doesn’t seem like there will be any easy way to combine these capacities into a good definition of what it is to be alive.

Feldman then goes on to discuss modern-day variants of Aristotle’s strategy. He argues that these modern-day definitions of “life” also either incorrectly exclude some living things, or else incorrectly include many dead things.

In Chapter 3, Feldman turns to a different strategy for defining life. This strategy is sometimes called vitalism. What’s distinctive of vitalists is that they think of being alive as a matter of having some special thing or substance, that is one’s life. On some accounts, this thing would be called “vital fluid.” On other accounts, it would be called a “soul.” (This is like our discussions earlier in the semester, where “soul” was also a word for a special kind of substance; but whereas before souls were what gave some things the ability to think and feel, now souls are instead what makes things alive. So different in some ways than before.)

Vitalists propose that being alive is a matter of containing some special life-substance. Their opponents will say that life doesn’t consist in the presence of any special substance. Instead, being alive is a matter of having some distinctive properties or abilities. Being tall is an example of a property. It’s not a substance. Instead, it’s a way for a substance to be. The Aristotelian strategy that Feldman considered in Chapter 2 tried to define being alive in terms of having a distinctive combination of properties or abilities. The vitalists, on the other hand, say that being alive is a matter of containing a special life-substance.

• We don’t have any good scientific evidence that there are such life-substances. (Or at any rate, some of them.)
• If Jonah is inside a dead whale, the whale would then contain a life-substance (Jonah’s), but would not be alive.
• The best response to the Jonah objection makes being alive not a matter of containing, but rather a matter of being animated by a life-substance. But on this definition, it doesn’t seem like the “life-substance” is doing any explanatory work anymore. Now it seems like the notion of “animating” is doing all the work. Why do living things have to be animated by life-substances, in particular? Is there anything conceptually impossible about being animated by something else?
• Wouldn’t it be at least conceptually possible to discover some Martians, that acted as though they’re alive, but which turn out not to have any vital fluid, or souls, or whatever we say life-substances are? Should we allow that they would be alive, after all—and hence vitalism must be wrong? Or should we stick to our vitalist definition, and say if they don’t have life-substances then they’re not alive? Feldman argues that the first response is more reasonable.

Feldman then goes on to discuss some modern-day versions of vitalism, which try to define life in terms of possessing DNA, or genetic information, rather than possessing a life-substance. He argues that these modern-day definitions are open to some of the same kinds of objections as the older vitalist definition.