4.2 Explanation 137
4.2 Explanation
In this chapter we return to an important
concept that was introduced in Chapter 2.8,
namely explanation. Explanation, like
argument, involves giving reasons. But
explanatory reasons do not lead to
conclusions, as reasons do in arguments.
Examine the following short passages.
[1a] Seawater is salty. This is because the
river water that drains into the oceans
flows over rocks and soil. Some of the
minerals in the rocks, including salt,
dissolve in the water and are carried
down to the sea.
[1b] The river water that drains into the
oceans flows over rocks and soil. Some
of the minerals in the rocks, including
salt, dissolve in the water and are
carried down to the sea. Consequently
seawater is salty.
These are both explanations. To be more
precise they are the same explanation, with
slightly different wording. Typically,
explanations tell us why something is as it is,
or how it has come about. The explanation
here consists of two reasons: (a) that rivers
flow over rocks and soil; and (b) that the rocks
and soil contain minerals that dissolve in the
water. These two reasons, between them,
explain a fact, the saltiness of seawater. But the
saltiness of seawater is not a conclusion or
inference drawn from [1a] and [1b]. Most of us
don’t need any argument to convince or
persuade us that seawater is salty. We have the
evidence of our senses. We can taste it, which
is a good enough reason to take it as fact.
This is the key difference between an
argument and an explanation. Arguments are
meant to give us reasons to believe something
which we did not know, or were less sure of,
before hearing the argument. That is what we
call a ‘conclusion’. Explanations work in the
opposite direction: they take something that
we know or just assume to be true, and help us
to understand it. Explanation plays a very
important role in science; and it is easy to see
why. One of the main goals of science – if not
the main goal – is to discover how and why
things are as they are: what causes them, what
makes them happen. Once we can fully
explain something, such as the saltiness of
seawater, we can go on to predict or infer all
sorts of other related facts or phenomena.Need for explanations
Explanations are particularly useful when
there is something surprising or puzzling that
needs to be ‘explained away’; or where there is
a discrepancy between two facts or
observations; or where there is an anomaly in
a set of facts. (An anomaly is an exception:
something unexpected or out of the ordinary.)
If a patient’s blood pressure is being
monitored, and on a particular day it is much
higher or lower than on all the other days, that
would be classed as an anomalous reading, and
might well lead the doctor to look for or
suggest an explanation.
Here is an observation that would seem to
be at odds with [1a] and [1b]:[X] River water does not taste salty.We are told by the scientists that seawater gets
its saltiness from the rivers that flow into it. So
why can we not taste the salt in the river?
Unless you know the explanation, there
appears to be a discrepancy here: if one tastes
so strongly of salt, why does the other taste
fresh? By analogy, if you poured some water
from a jug (the river) into an empty bowl