I’m sure that we have all seen it happen at one point or another. Two people are debating about some scientific topic and the person who is opposed to the mainstream scientific view gets backed into a corner by an opponent who is wielding numerous peer-reviewed studies, so how does he get out of it? Simple, he merely utters the words, “well scientists have been wrong in the past, so they might wrong now,” and having spoken those irrefutable words, the debate ends, and the anti-scientist leaves, thinking himself victorious. In reality, all he did was use a logically invalid cop-out that does nothing other than demonstrate how truly weak and indefensible his position is.
The first problem with this argument is simply that it is a guilt by association fallacy (or ad hominem depending on exactly how it is used). Just because scientists have been wrong in that past does not mean that you can blindly reject all evidence and arbitrarily assume that they are wrong now. So right off the bat, the rules of logic tell us that this argument is no good.
The second problem is one of the most important. Of course scientists have been wrong in the past, because science is inherently a process of proving other scientists wrong. That’s how science works. It would be a terrible thing if scientists were never wrong because that would mean that science had come to a standstill and was no longer advancing. Here’s the important thing though, scientists are always proved wrong by other scientists! No major scientific principle has ever been overthrown by someone with no scientific training sitting on their couch and speculating! New scientific discoveries are made by scientists, not bloggers, not people who have never set foot in a lab. There is no universe in which someone’s uneducated opinion is just as valid as the results of countless peer-reviewed studies.
Next, we arrive at a core problem with the fundamental claim of this argument. More often than not, I hear this argument accompanied by a claim like, “scientists used to think that the earth was flat,” but did scientists really think that? You see, the term “science” is relatively new. Virtually all of the examples that I hear of flawed views that scientists supposedly held are from a time period that predates science as we know it. Science today is very careful, systematic process that allows us to be highly confident in our results. The statistical analyses that allow us to quantitatively test our hypotheses, for example, have only existed for the past 100 years or so. There is simply no comparison between the “scientists” who thought the earth was flat and the scientists today. The “scientists” back then were no different from alchemists. They were not employing the rigorous scientific methodologies that we use now.
So if we are going to make the claim “that scientists have been wrong in the past, therefore they shouldn’t be trusted today” we have to limit ourselves to roughly the past 100 years. Now let’s ask the question, “have scientists been wrong about anything in the past 100 years?” Well yes, of course they have been wrong about a lot of things. The past 100 years have seen great advancements in almost every field of science as new discoveries have replaced outdated hypotheses, but keep in mind that this argument is used against scientific theories and concepts that have an overwhelming amount of evidence behind them. It isn’t used against a particular cladogram showing the evolutionary relationships between turtles, rather it is used against the entire theory of evolution. It isn’t used against a particular model of climate change, rather it is used against the very idea that man could change the climate. So the question is really, “in the past 100 years, have scientists been really wrong about something very important that they were extremely confident on (something on the level of the theory of evolution or the usefulness of vaccines)?” The answer is…not really. The modifications that Einstein’s theory of relativity made to Newtonian physics is really about the closest example, but even then, Newton wasn’t wrong so much as incomplete, and relativity was proposed at the very beginning of the 100 year period we are talking about. So when you actually stop to think about it, the core claim of this argument isn’t even correct.
The next objection to this argument is perhaps the easiest for most people to grasp. If this argument worked, than we could use it in absolutely any situation. “You think the earth moves around the sun? Well I think the sun moves around the earth, and scientists were wrong about the shape of the earth, so why should I trust them about its movement?” You see the problem here? If we allow this argument, then we can’t ever trust science about anything!
This leads to the final problem with this argument. It actually creates a logical paradox that destroys itself. Consider, the argument posits that we can’t trust scientists because they’ve been wrong in the past, but the only reason why we think those scientists were wrong was because other scientists discredited them, but we’ve just established that we can’t trust scientists, which means that we can’t trust the scientists who discredited the original scientists. By way of example, why should I trust the scientists who say that the earth is round instead of the ones who say its flat? This argument (if it worked) would make all science invalid and we would have no reason to accept anything that any scientist has ever discovered (which is clearly absurd).
In conclusion, despite being one of the most common anti-science arguments, this claim has a logical fallacy as its core, it is based on a faulty understanding of science, and it unravels everything into a chaotic mess in which science can never tell us anything. All of which clearly shows that this argument is entirely invalid and should never be used.