- Since the concept of life apparently plays a role in the definition of death, we must first understand what is meant by 'life'.
- In Chapters 2 and 3, I present several of the most plausible accounts of the nature of life. I attempt to show that each of them fails. Life itself turns out to be a bit of a mystery.
Life itself 
- The "life" we’re interested in is the property possessed by all living things. NOT to be confused with:
- the "history3" of a living thing ("his life was filled with joy/lasted 82 years") – the life we’re interested in is not tied to duration
- the different lives of people – the life we’re interested in is the same for all living things
- the aggregate of living things (life on earth, "teeming with life")
- metaphorical usage ("the hills are alive…")
- Are ponds living things? Is the Gaia Hypothesis (that the Earth is alive) right? (No and no, says Feldman)
Some Preliminary Objections 
- Mayr: "Life is simply the reification of the processes of living … there is no such thing as an independent ‘life’ in a living organism".
Response: the fact that life is not a substance or force doesn’t mean it’s not a property – analogy with "motherhood". It may not be something measurable by science but that doesn’t mean it doesn’t exist.
- Living things are so varied that there is no one thing they have in common.
- (a) they do have something in common "they share all necessary properties and they are all alive" [isn’t this begging4 the question?]
- (b) huge variation doesn’t rule out the possibility of similarity – again, the class of "mothers" (bugs, humans, whales)
Aristotle’s Life-Functional Analysis of Life 
- Suggested life-functions:
- Nutrition/reproduction (most basic, possessed by all living things)
- Sensation (only possessed by living things, but not by plants)5
- LF1: x is alive at t =df. x is able to perform at least one of the life functions at t
Objection: TOO BROAD. One of the life functions is motion, and robots have it.
- LF2: x is alive at t =df. x is able to engage in nutrition and reproduction at t
Objection: TOO NARROW. Many living things cannot reproduce (too old, too young, mutilated)
- LF3: x is alive at t =df. x is able to engage in nutrition at t
Objection: STILL TOO NARROW. The cecropia6 moth cannot eat.
- LF3’: x is alive at t =df. either (i) x is able to engage in nutrition at t or else (ii) x was able to engage in nutrition at some time earlier than t
Objection: Now TOO BROAD. Includes dead7 things.
Some Modern Life-Functional Analyses of Life  - The genetic analysis of life [NASA]:
- LF4: x is alive at t =df. x is able to reproduce at t, and x is able to produce and perpetuate genetic variation among offspring at t
Objection: TOO NARROW. See objection to LF2, and also many ants and bees are never able to reproduce (and no individuals are able to mutate!)
- move discussion to talk of species. Although individual ants and bees cannot reproduce, it must be the case that ants and bees as a species must be able to reproduce and mutate.
- A species is variably reproductive if some of its members can reproduce offspring that manifest small genetic differences from their parents.
- LF5: x is alive at t =df. x is a member of some variably reproductive species at t
- Objection (1) : TOO BROAD. Includes dead things ("a dead chicken is still a chicken")
- Objection (2) : uses the "notoriously obscure" concept of "species"
The Matthews Approach 
- Life functions are capacities without which a species cannot be preserved. Suggested examples: reproduction, reason, sense perception, locomotion, appetite, metabolism
- LF6: x is alive at t =df. at t, x is able to exercise at least one capacity that is a vital function for x’s species
- Objection (1): Unclear. What does it mean to say "without which a species cannot be preserved"? Does this mean that every member of the species must exhibit that capacity for the species to be preserved? Clearly not (ants and bees for reproduction). So in that sense it cannot even be that members of the species in general must exhibit a property for it to be a life function. (That is: individual ants and bees do not need to reproduce – in fact only one female in ten thousand engages in reproduction – yet those ants and bees are clearly alive. But Matthews only says they must exhibit one of the capacities. Can an individual be living without displaying reason, sense perception, locomotion, appetite, metabolism and reproduction?)
- Objection (2): TOO BROAD. Combustibility is a life function for some evergreens, but it is possessed by dead trees.
- Objection (3): Either covertly CIRCULAR or TOO BROAD again. "Alive" is defined in terms of life functions. Life functions are defined as those without which a species cannot be preserved. But what is the definition of "preserved"?
- Suggestion 1: S is preserved up to t = df. S still exists at t
- (a) species are defined as properties (that is, the species "tiger" is the property of being a tiger, in which case they exist whether or not individual members exist, just as "redness" would still in some sense exist even if all the red things were destroyed), which in this case would mean that there are no life functions, because nothing is required to keep a species existing (just as nothing is required to keep "redness" existing), or
- (b) for a species to continue to exist, individual members must exist. In that case:
- Suggestion 2: S is preserved up to t = df. there are still some living members of S at t
Objection: But this is flagrantly circular, because "preserved" is defined using the term "living", when we were trying to define living in terms of "preserved". What if we replace "living" with "existing"? That is:
- Suggestion 3: S is preserved up to t = df. there are still some existing members of S at t
Objection: But dead individuals still "exist" – there are even existing examples of dodos. This would make the definition TOO BROAD.
- The life-functional approach to the analysis of life is unsuccessful8. I see no satisfactory way to define life by appeal to some set of life functions.
Footnote 1: Taken from "Feldman (Fred) - Introduction: Confronting the Reaper".
Footnote 2: Taken from "Cushing (Simon) - Fred Feldman: Confrontations with the Reaper".
- See my Note on Life (Click here for Note)
- This distinctions between biological life, and the career or history of individuals that may or may not be biologically alive is important, and frequently confused by Baker.
Footnote 6: I’m not convinced of the value of pressing definitions with very unusual cases. See previous comment.
- Yes, it is, and I agree that Life might be a “family resemblance concept”, like “game”, where there is no set of necessary and sufficient conditions that anything we want to call “alive” must satisfy.
- This style of analytical philosophy can appear rather nit-picking and sterile. This comment applies to much of the book.
- A lot of problems are caused by Feldman’s belief that dead things are of the same kind as the things they are the corpses of.
- We’re trying to distinguish live things from dead things (as well as from inanimate things), which will be hard if the things in the two states are taken to be of the same kind.
- Well, you’ll need to try harder then (or give up on “dead things”)!
- The “life-functions” approach is the obvious “scientific” approach to biological life. Vitalism (see the next chapter) is a non-starter.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2020
- Mauve: Text by correspondent(s) or other author(s); © the author(s)