MORE EFFECTIVE REASONING II: BETTER LINKS 75conventional sense of good dress', then, clearly, the claims about his hat, trousers,
and bare chest would be relevant. What determines the easy judgment that a is a
good argument and b is a bad argument is the implied premise 'physical symptoms
are relevant evidence from which to induce a conclusion about physical health'.
Indeed it is so obvious—in our society, but perhaps not others—that we would be
thought odd if we actually explicitly stated that premise.
Relevance is often a major problem in argumentation. Poor arguments regularly
report the 'facts' well, and try to draw conclusions from them but do not establish the
relevance of the premises given to the conclusion asserted. Poor skills in reasoning,
especially not identifying one's assumptions, are one cause. As we considered in chapter
4 one of the functions of premises is, precisely, to establish relevance—not something
which all people who use reasoning realise. However it is not just a problem of
technique. Often the debates in our society that are most difficult to resolve concern
disagreements about whether or not a premise is relevant to a given conclusion.
Consider the treatment of people who arrive as refugees in Australia directly, rather
than by official routes (so-called 'illegal immigrants'). Politicians who support deten-
tion of these people argue that international laws concerning the proper treatment of
refugees are not relevant to this class of immigrants because they have arrived illegally.
Opponents of detention counter by saying the international laws are relevant. On both
sides, there is agreement that there are such laws, and that they do prohibit detention;
there is also agreement that people are arriving in this manner. What differs is the
judgment as to whether or not the refugees are arriving legally or illegally and, in
consequence, whether human rights conventions are or are not relevant.
Issues of relevance are rarely as obvious as the example about Smith and his
health that I used at the start of this section. Smart thinking always involves very
careful consideration of relevance as distinct from whether or not premises are well
founded. To emphasise, relevance of premises is completely different from the
acceptability of premises. A claim can be true (and thus acceptable), but this quality
alone does not necessarily mean it is relevant to the conclusion. For example, it is
definitely the case that, as you read these words, the claim 'You are reading this
book' is true and acceptable. But is it relevant to the conclusion 'You are going to
cook fish for dinner tonight'? No! Hence, in making our arguments and explana-
tions effective, we should not be satisfied simply that our premises are acceptable
in themselves: for them to give any support to the conclusion, they must also be
relevant to it. So, put simply, a premise is relevant to the conclusion when it
provides some basis on which to decide whether or not to accept that conclusion.
Exercise 6.2
To help you to learn about relevance, let us look at some examples. In the
following arguments and explanations, decide which premises are relevant to the
conclusion (which is italicised in each case):
a. Why did the train crash? The train was going too fast and its brakes were
faulty; also, there were many people waiting at the station.