Philosophy of Biology

Functions 531

of the radiator. In short, function statements explain the presence of

functionally characterised artefacts. Function statements also explain

the presence of functionally characterised traits. When we say that the

function of the sail on the back of Dimetrodon is to regulate heat, we

also give an answer to the question ‘Why is the sail there?’, and we

thereby explain the presence of the sail.

Functions can be distinguished from accidents:Artefacts have all kinds

of useful effects that are not their functions. These have come to be

known as ‘accidents’, or accidental benefits. A bible kept in a breast

pocket might have the beneficial effect of deflecting an otherwise deadly

bullet, but that is not what the bible is for. The bible is for spreading

the word — that is its function, and the preservation of life is only

an accident. Once again, what goes for artefacts goes for organisms.

Organic traits may have plenty of beneficial effects that are not their

functions. The standard example is that of heart sounds: human hearts

make noises, which can often benefit their bearers by assisting doctors

in making diagnoses that lead to subsequent medical treatment. But

making diagnostic noises, although an effect of hearts, is not what they

are for. Hearts are for pumping blood.

Functions statements are normative: Function statements do not de-

scribe how an artefact is behaving; rather, they describe how it should

behave. A CD player that repeatedly skips has the function of playing

music, even though it cannot play music. It makes sense to say that

the CD player has gone wrong, or that it is malfunctioning, because

the CD player continues to have a function even though it cannot per-

form that function. Similarly, to say that the function of the eye is

to assist in vision is to say what eyes ought to do, even though some

eyes may have this function and be unable to perform it on account of

being clouded by cataracts.

It is largely because of a conviction that any account of biological functions
must justify these connotations of function statements by reference to biological
facts alone, that many philosophers have rejected what has become known as the
Causal Role (CR) account of functions. The Causal Role account, which we owe
to Robert Cummins [1975], vies with the SE account for attention in most current
work on functions. On Cummins’ view, function attributions feature infunctional
analysesof complex systems. Functional analyses explain the capacities of a sys-
tem (whether that be a washing machine, a car, the mammalian reproductive
system or the Belgian economy) by reference to the contributions of the system’s
heterogeneous parts. The CR account says that an item’s functions are the con-
tributions that it makes towards a capacity of a containing system. The questions
of which containing system, and which capacity, are the relevant ones by which to
attribute functions are decided by the interests of the investigator. So on this view,
the function of the heart is to pump blood because, in the context of the capacity