This week I am going to look at the ad populum fallacy. Ad populum is Latin for “appeal to the people”. This fallacy occurs when a person argues that a particular claim is true because a large number of people accept it. Put crudely it contends that a position is true because it is popular – a majority of people, or a majority of one’s peers accept it.
Appeals to what others think have an important psychological influence on us because we are social beings and fitting in with one’s peers and the society around is important to us. Taking a view that is unpopular risks putting us at odds with others; in some circumstances it can lead to social alienation and ostracism – people risk being ridiculed, shunned or demeaned. Our desire to avoid these sorts of responses by others can lead us to not question certain claims or to accept others.
In fact often it is this kind of pressure that is deliberately used to try to influence people into accepting a claim is true. When I studied at University, it was far more common to hear people attempt to dismiss Christianity by claiming it was out of accord with what contemporary people think or that it was old fashioned and so on, than it was to hear any actual argument against Christianity.
Unfortunately popularity is not the same thing as truth. If a claim is popular it tells us that a large number of people think it is true. However, a claim is true when what it affirms is, in fact, the case. It is possible that what a large number of people think is the case is not, in fact, the case. Majorities can be wrong and throughout history have been. False ideas, bigotries, prejudices, urban legends and superstitions can be widely held and popular in a society.
As I noted in Analysing Arguments, an argument is valid when it is impossible for the conclusion to be true and the premises false. Given it is possible (in fact, it is often actual) for a popular claim to be false, inferring that a view is true because it is popular is a fallacy.
This past week Philosopher and Theologian William Lane Craig and Physicist Lawrence Krauss, debated the moot “Is there Evidence for God?” at North Carolina State University (video and MP3 available at the link). At one point during the debate, Krauss stated that 90% of the American academy of sciences did not believe in God; this, he argued, provided good reason for thinking there was no evidence for God’s existence.
This example highlights some subtleties in how this fallacy should be applied. Krauss suggested that there is no evidence for God’s existence because the vast majority of scientists do not believe in God. In support of this he stated that the vast majority of those who have studied the evidence contend that the evidence is not there. Krauss was arguing for a position on the basis of what the majority of the experts in a field think. On the face of it, there does seem some merit to this; surely, if the majority of experts in a given field — the majority of people who have spent years researching it and whose knowledge of this particular field is incontestable – believe something particular about that field this provides reasons for us thinking that what they believe is true. Doesn’t this seem right?
Here two caveats must be issued. First, any attempt to argue for the conclusion that a claim is true from the fact that the majority contend it is will always be invalid because it is possible that the majority of experts will be wrong. This is true even in the sciences. But, of course, one might not be attempting to argue for a conclusion merely on the basis that a particular position is widely endorsed by the experts, one could instead be suggesting that expert consensus creates a presumption in favour of the claim in question. If the majority of experts in a field believe X then in the absence of reasons to the contrary the sensible thing is to accept X. This kind of view grants that it is possible that the experts are mistaken but it suggests we should not assume they are unless we have good reason for thinking this; the burden of proof is on the one who goes against the consensus.
There may be something to this, however, even if one grants this a second caveat needs to be noted. This presumption only applies if the group in question are, in fact, experts in the relevant field. Consider an example that Alvin Plantinga provided in a talk at the recent Evangelical Philosophical Society conference in Atlanta. Plantinga asked “if the majority of scientists hate new Zealand does it follow that hatred of New Zealand is scientific?” The answer is, obviously, no and the reason is that the question of which countries one likes or dislikes is not really an issue for scientific investigation. Moreover, even if there were a technical discipline that gathered data about different countries and compared them, the vast majority of scientists, physicists, biologists, astronomers, chemists and so on, would have little or no expertise in this discipline. Hence, the mere fact that the majority of scientists believe a particular conclusion on their view of New Zealand is of no more significance that the fact that a majority view of any other group on this topic.
This is where I think Krauss’ argument falls down. Krauss suggests that scientists are the group of people who have the best expertise when it comes to the evidence for and against God’s existence. This seems false. In the debate Craig offered five arguments for God’s existence; two were philosophical. Of these, one drew upon claims from physics in one supporting argument for one premise and another appealed to a finding of physics as a premise. The arguments for each of the inferences from physics drew metaphysical and philosophical claims by utilising other philosophical premises. The third argument Craig offered was purely meta-physical and looked at the relationship between contingency and necessity. The fourth argument was about what is the best meta-ethical theory. The fifth was an inference drawn from claims made by historians and biblical scholars. Is it really plausible to contend that scientists, as a group, are “experts” in these areas – very little of which are science? Most scientists will not have spent much time studying these things. What would be more relevant would be what the majority of Philosophers of Religion believe – this is a discipline, after all, that does study the arguments for and against the existence of God.
But even if the majority of experts in a relevant field do hold to a claim and one does grant this claim, this creates a presumption in favour of the claim, albeit a defeasible one. The point is that this is a presumption. It holds in the absence of reasons to the contrary. As soon as one faces a situation where someone offers an argument against the claim, one needs to ask wether the presumption has been overturned and defeated. One cannot answer this by simply citing the presumption.
These caveats point to a final and all important issue. The issue is not so much what the majority of people think but whether they have good reasons for thinking it. The authority of a popular consensus amongst a group of people is parasitic upon the arguments, research and so forth of that group. The reason people think scientific consensus counts is because they think science counts – they believe these people are experts in and have utilised a reliable method in coming to their results. Appeals to popularity therefore have head-way only in a context where this assumption is reasonable. What this shows is that, in the end, it is not the popularity of a view that matters, it is whether there are sound arguments for accepting it. The mere fact a view is widely held is, in and of itself, irrelevant to the truth or falsity of a position as it tells us nothing about whether an argument for or against a position is sound.
Every Friday I publish another post in my Fallacy Friday series. To navigate the whole series, use the Fallacy Friday tag.