So far, we have talked vaguely about reasons for belief. Often, we call these reasons, evidence. But what exactly is the relationship between a person, evidence, belief, and the truth of a proposition? For instance, our belief that Jesus rose from the dead has some relation to evidence and truth. But what is it? Evidentialism attempts to provide an answer. In short, an evidentialist claims the following:
Evidentialism: S has good reasons to believe p and S believes p on the basis of those good reasons.
Evidentialism is a common-sense view, and, to some extent, we assume it for most of our ordinary beliefs. An evidentialist argues that the normative relationship between a person, a belief, and the evidence is that (i) the total evidence available to S supports the belief that p at the time at which she possesses that evidence and (ii) S believes p on the basis of that evidence.
The first component has to do with evidence and its relation to what one believes (the proposition). The evidence should make it more likely for the proposition to be true than not. But what exactly constitutes support?
Suppose a friend tells you that the best plumbers are called Joe. You ask your friend for some evidence. In response, your friend says the name Joe out loud to you as if to get you to hear that it is the name of good plumbers. Then he writes it down and says, “you see? Just look at the name!” Of course, the sound and look of a name doesn’t support the belief that the best plumbers are named Joe. So, what is lacking here?
To answer this question, we return to a twofold means for assessing arguments. The first question to ask is: does the belief follow from the evidence? There are at least two ways it can fail to do so. The first has to do with the relevance of the evidence to the proposition. In our best plumber example, it is difficult to see how the sound or look of the name Joe has anything to do with the best plumbers. It is simply irrelevant.
The second way a belief might not follow from the evidence is by being insufficient. In other words, the evidence might support something but not as much as the conclusion says. Suppose our friend adds to his case that Joe is a very common name among people who tend to take on plumbing work. Suppose he supplies some empirical research to that effect. The evidence he has presented now shows something. Perhaps it shows that there is a higher frequency of plumbers named Joe compared to other names. But it doesn’t show that the best plumbers are named Joe. Insufficient evidence proves something, but it falls short of proving the proposition in question.
The other question to ask about evidence is whether it is likely to be true. If one bases one’s beliefs on false propositions, then those beliefs are not supported. Our friend’s false plumber belief is based in part on the sound and look of the name being great-plumber-like. But it is simply not true or, at the very least, grossly unsupported, that the look or sound of the name is plumber-like. Hence, the belief is not supported.
Falsehoods can’t act as support even if what they support turns out to be true. Suppose by an amazing coincidence, our friend’s plumber-belief turns out to be true. Unbeknownst to us, a survey was conducted and published showing that the best plumbers are called Joe. Although our friend might be somewhat justified in conducting a little bit of I-told-you-so, the reasons he had for his belief remain false. The most we could praise him for is his remarkable luck! We would not have to concede that his argument was a good one.
The second component of evidentialism has to do with a mental process in the mind of the believer. Of course, there could be lots of good evidence for a proposition, but no one has noticed it. Hence, in addition to a good relation between evidence and a proposition, a believer must form her belief on the basis of that (good) evidence. Doing so is often regarded as having a well-founded (or well-formed) belief. A well-founded belief is one that S believes for the right reasons.
The evidentialist approach highlights an important aspect of our responsibility for our own beliefs. In scrutinising our own beliefs, we should be concerned with making sure that we believe for the right reasons. We should examine the evidence we have for its relevance, sufficiency, and truth. In addition, when making a case for our beliefs to those who don’t believe, we should also be careful to avoid using evidence that doesn’t have anything to do with our beliefs, claiming more than we can prove, or using false (or unsupported) evidence.
For more on evidentialism, I suggest reading Richard Feldman’s Epistemology. As well as providing a good description and defence of evidentialist thinking, it is also an excellent introduction to the other topics in epistemology. John Feinberg’s excellent book, Can You Believe It’s True? continues to provide me with an excellent source of answers to questions about epistemology in our attempt to defend our faith. On pages 149 to 153, Feinberg cautions us to make sure our evidence actually supports what we claim and how to avoid making this mistake in an apologetic setting.