The Truth Norm Account of Justification
What makes beliefs rational or irrational? This question can be illustrated with some examples of irrational beliefs. Particularly striking examples are beliefs in conspiracy theories. In a 2012 YouGov poll of British adults, 12% of respondents said they believed that the 1969 Apollo moon landings did not happen, 17% said they believed Lee Harvey Oswald did not assassinate John F. Kennedy, and 24% said they believed Princess Diana was assassinated. These seem to be clear examples of beliefs that are irrational. But what makes them irrational? Is it because they are not true? Or is it because they are not supported by evidence?
On the one hand, both of these explanations seem plausible. Indeed, there seems to be a close relationship between the two explanations. It seems that the fundamental point of having a belief that is based on evidence is to have one that is true.
On the other hand, these two explanations also seem to conflict. This is because sometimes evidence can be misleading. In such cases, a belief might be well supported by the evidence, but still fail to be true. For example, it’s plausible that before Galileo observed the phases of Venus, the available evidence supported the belief that the sun and the other planets rotated around the earth. But that belief was false. Misleading evidence like this raises doubts about the relationship about between evidence and truth. If the fundamental point of believing what the evidence supports is to believe the truth, how can it be the case that believing what the evidence supports sometimes results in believing falsely?
My PhD thesis provides a way out of this problem. It offers an account of the relationship between epistemic rationality and truth which is consistent with the possibility of misleading evidence. I argue that epistemic rationality is explained by a truth norm, a rule which states that one ought to believe something if and only if it’s true. To see how a truth norm like this explains rationality, note that one cannot follow a truth norm directly, i.e. one can’t ‘just tell’ whether one’s beliefs are true or compare what one believes with what is true. One is going to have to take some indirect means to try and ensure that one’s beliefs are in accordance with a truth norm. And it seems this would involve ensuring that one believes something if and only if one has evidence that it’s true. Therefore, the means one has to take in order to follow a truth norm, given one can’t tell directly whether one is in accordance with it, will sometimes involve having false beliefs that are supported by the evidence.
If you want to read more, you can download my thesis from here.