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:

X dies at time t =def X ceases to be alive at t.
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:

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." (Later we'll be looking at more narrow definitions of what "souls" are.)

To understand what the vitalist is proposing, we need to get clear on what this notion of a substance is. Consider the following examples.

Claire has a sharp knife. Claire has a sharp wit.
Once you climb the steep cliffs on this side, you'll find a gentle slope down to the plain. Despite his harsh words, Mike has a gentle touch.

Let's look first at the first column. It says that there is this thing, a knife, that Claire possesses. And there is a thing, a slope, on the other side of the cliff.

But now in the second column, when we talk about a sharp wit and a gentle touch, we don't seem to be talking about things in the same way. Well, in one sense they are things. I can say, "There's one thing I really like about her, that's her sharp wit." But Claire's wit doesn't seem to be a thing in the same robust, full-blooded way that a knife and a slope are things. Philosophers use the term substance when they're talking about things in this robust, full-blooded way. Knives and slopes are substances, but wits and touches aren't.

Substances don't always have to be solid things. It's philosophically controversial what substances there are; but arguably clouds and liquids are also substances. Substances don't have to be things you can touch and feel. Campfires may well be substances; and so may be the oxygen they consume. Perhaps there are even non-phyical substances: if there are any ghosts flitting about the campfire, then they would be things, too, in the full-blooded sense in which knives and campfires and oxygen are things. I'm not saying there definitely are any non-physical substances. But there's nothing in the philosopher's definition of "substance" to rule them out. At least, there isn't obviously anything there. If ghosts are to be ruled out, it will take further argument or reasons to do it.

There seems to be some intuitive difference between: knives, slopes, clouds, fires, oxygen, and ghosts, on the one hand, and wits and touches, on the other. The former seem to be "things" in a robust and full-blooded sense in which the latter don't. Philosophers put that by saying that only the former things count as substances.

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.

Feldman presents the following objections to vitalism:

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.