4.2 Explanation 139
Don’t jump to conclusions
You saw both in the previous chapter and in
Chapter 2.10 that some of the worst reasoning
errors come from jumping to conclusions.
This is a particularly strong temptation when
inferring causal explanations. Suggesting
explanations is fine. Assessing their
plausibility is fine. But just because an
explanation is plausible it doesn’t follow that
it is true. If it were a fact that Darius had a huge
but poorly trained army, that could explain the
Persian defeat at Issus. But so might good
training explain the Macedonian victory.
Moreover, it might be neither of these. It
might be something quite unlikely.
Conceivably the battle was determined by
Alexander’s mother casting a magic spell, or
laying a curse! This may seem fanciful and
implausible. We don’t really believe these days
in spells and curses as real causes. But
sometimes the wildest theories turn out to be
correct. It is fairly well documented that in
ancient times people were much more
superstitious than they are today. Oracles and
soothsayers were taken seriously and consulted
before decisions were made; witches were
burned for the evil powers they were thought
to possess. Had a spell been cast, and believed,
the psychological effect could have been quite
potent. It might have filled one side with
confidence, and/or the other side with terror.Judging alternative explanations
It is all very well to say that if something were
true it would explain a fact. The mistake is to
move too quickly from the discovery of a
satisfying and credible explanation to the
inference that the explanation is true.
Explanations need to be evaluated just as
critically and carefully as the reasoning in an
argument. In the case of explanations we are
looking for the best. What makes one better
than another?
There are two useful tests for judging the
effectiveness of an explanation. One is to
question its scope; the other its simplicity. Theexplanations which, if true, would explain the
outcome of the battle, against all the odds.
Alexander may have used better tactics. He
may have had better weapons. He may have
been a more inspiring leader than Darius.
The small numbers may have made the
Macedonian army more mobile, easier to
command. The Persians may have been tired,
or sick, or suffering from low morale. They
may have been overconfident because they
had more soldiers and were taken by surprise
by the ferocity of their enemy, and so on. One
or more of these possibilities could have been
sufficient to change the course of the battle
away from the foregone conclusion that most
people would have predicted. We cannot say
which, if any, really was a factor, still less
the decisive factor, on the day. All we can say
with certainty is that there are competing
hypotheses. But we can make some valid
judgements: we can assess the competing
explanations in terms of their plausibility. We
can ask, of a proposed explanation: Would it,
if true, have explained why the battle went
Alexander’s way? If the answer is yes, it is a
plausible explanation, even though we cannot
infer that it is the explanation.
Conversely, we can say that certain
statements would not adequately explain the
outcome even if known to be true. The fact
that Alexander’s soldiers were Macedonian is
not an adequate reason, though it is a fact. It
might be adequate if we also knew that
Macedonians were particularly skilled or
ferocious or dedicated fighters; but on its own
the fact of being Macedonian does not explain
their victory. Similarly, if we were told that
Alexander later became known as ‘Alexander
the Great’, that would not explain the victory.
It is his victories which explain why he was
called ‘the Great’. Nor would the fact that
Darius’s soldiers fled when they realised they
were beaten count as an explanation: it would
just be another way of saying that they were
defeated, not a reason why.