PLAUSIBILITY OF CLAIMS

Another important question to ask when evaluating evidence is ‘how plausible is this
claim, or piece of evidence?’
We need to clarify what is meant by ‘plausible’ in this context, in particular to make
clear the difference between questions about plausibility of evidence and questions about
reliability of evidence. We have already used the word ‘plausible’ in relation to
explanations. In that context its meaning was ‘possibly correct, or likely to be correct’.
Sometimes in everyday speech the word plausible is applied to someone’s manner. For
example, members of a jury may judge a defendant ‘plausible’ and therefore be inclined to
believe their statements, on the basis of their speech, facial expression and body language,
rather than on the basis of a process of reasoning. It is possible that human beings are very
good at making accurate judgements of character on this basis, but they are not using
critical thinking skills when they do this. Of course, it is also possible that someone could
use a process of reasoning to judge plausibility in this sense, if there were well-established
criteria which indicated when individuals were lying. So in critical thinking texts and
examinations, a question could in principle be asked about the plausibility of a particular
person, based on evidence of their behaviour.
However, in general when questions about plausibility of evidence are asked in critical
thinking texts, the question refers to the plausibility of what is said or claimed, and not the
plausibility of the person who says it. Thus the question ‘Is Ms Brown’s evidence plausible?’
should be interpreted as meaning ‘Is Ms Brown’s claim the kind of thing that could
be true, or could have happened?’