How Do We Decide Between Contrary Expert Opinions?

Expert testimony is a vital source of evidence. Without it, we know little because much of the information available on any subject comes through the testimony of field experts. Knowledge of anatomy, history, neuroscience, and even spiritual formation, in fact, are dependent on expert testimony. Indeed, the Bible itself is God’s testimony to humanity. To ignore testimony is to undermine most of what is known.

In answering the question of how we can decide between contrary expert opinions, we must first recognize that someone can be an expert in one domain and lack expertise altogether in another. Parents, for example, may be experts on the preferences of their children, but they may know nothing about philosophy. Moreover, any expertise comes in degrees. Someone might have developed a degree of expertise about a subject without achieving the same level of expertise another person holds. No one, for example, would claim that the parent of one newborn is as prepared to answer questions on effective parenting as is a dedicated mother of ten.

In weighing contrary expert opinions, we must consider the relative levels of expertise possessed by the two experts discussing the question at hand. Relatively speaking, one should put more stock in the testimony of someone with more expertise.

Further, one should always weigh one’s own level of expertise relative to any disagreeing experts’ experience. To the degree that one is an expert in his own right, one’s own opinion should count for more in the evidential accounting. Insofar as expertise is a function of having evidence, this means that the more evidence one possesses that is independent of expert opinion, the less one should be concerned about conflicting expert testimony

Also important is whether one has reasons to think an expert rejects a relevant aspect of one’s own worldview—as would be the case in the previous example. To the degree that so-called experts reject one’s own worldview, one has less reason to trust their opinions about matters relating closely to those worldview commitments. If, for instance, an expert biblical exegete is known to reject the possibility of miracles, then one shouldn’t be concerned when that exegete claims that a passage about a miracle does not teach that there was a miracle.

If one is faced with expert A’s testimony, which conflicts with expert B’s, though both possess equal levels of expertise on the question at hand and share one’s general worldview, one should proceed with caution. To the degree that one thinks A and B have different levels of expertise, or one has evidence independent of A’s and B’s testimony, or one knows A or B or both reject fundamental aspects of one’s own worldview that are relevant to the question at issue, one ought to adjust one’s confidence either toward the view of the person with greater expertise who shares one’s worldview or toward the view supported by one’s independent evidence. In every case, we must remember that the Word of God is the highest and only completely trustworthy authority.