The Fallacy of Expert Witness

Andy Naselli reports on a very helpful section from Greg Koukl's new book, Tactics. He writes:

One of the most helpful chapters is entitled “Rhodes Scholar.” It’s one of eight chapters in part 2, which is devoted to finding flaws in arguments. In order to discern if an appeal to an authority is legitimate or if it commits the fallacy of expert witness, Koulk crisply distinguishes between information and education:

The ["Rhodes Scholar"] tactic hinges on the difference between informing and educating. When an article tells you what a scholar believes, you have been informed. When an article tells you why he holds his view, you have been educated.

Here is why this distinction is so important. If you recall from chapter 4, an argument is like a house whose roof (what a person believes) is supported by walls (the reasons why he believes). You cannot know if the reasons are adequate to the conclusions—if the walls are strong enough to hold the roof—unless you know what those reasons are. If you know the reasons, you can assess them. Without them, you’re stonewalled.

Popular articles always inform, but almost never educate. As a result, you have no way of evaluating a scholar’s conclusion. You simply have to take his word for it. But scholars can be wrong, and often are. Their reasoning can be weak, their facts can be mistaken, and bias can distort their judgment. (pp. 167–68)

The key, Koukl aruges, is simple: “Always ask for reasons. Don’t settle for opinions” (p. 168).

So how should we evaluate whether we should believe a expert’s opinion? Koukl suggests two ways.

[1]The scholar may be in a special position to know the facts. However, if an authority is in possession of special information that guides his counsel, then he should be able to point to that evidence to convince us he’s on the mark.

Sometimes authorities give opinions that are outside of their area of expertise. . . .

In a court of law, the expert witness is always cross-examined. Credentials alone are not enough to certify his testimony; he must convince a jury that his reasons are adequate. . . .

[2] Sometimes a scholar is in a unique position to render a judgment. More than mere facts are in play here. Interpretation is needed.

In this circumstance, you face another pitfall. A scholar’s judgment may be distorted by underlying philosophical considerations that are not always on the table. . . .

Sometimes one’s destination is predetermined by where one starts. (pp. 168–69)

I have been listening to Greg's talk show, Stand to Reason (podcast here), in recent days and would highly recommend his show and this book! He will help you think through how to winsomely engage with those who don't see Christ as worthy to be trusted.