Are You Certain?

Author’s note: In addition to publishing new posts weekly, I periodically republish “evergreen content”—articles that focus not on current events but on why we think the way we do, as well as on how we can think more and better than is presently the case. Today’s post was originally published on Aug 26, 2025. Enjoy! In these posts I have distinguished between belief, disbelief, and nonbelief. In this post, though, I will focus my attention on the act of believing. It is tempting to think that belief is a binary, all-or-nothing phenomenon, but this view is mistaken. This is because belief “admits of degree.” Allow me to explain. Belief is not like an old-fashioned light switch, either on or off. It is more like a modern dimmer switch that has degrees of “on-ness.” Or shifting the simile, it is like the wind. In the same way as wind has both a direction and a velocity, your beliefs have both content and a level of confidence. Consequently, whereas some people feel certain that Bigfoot exists, others think only that he might exist, while yet others think it highly unlikely that he exists. Not only do we tend to think of beliefs as being binary, but when others indicate their level of confidence in a belief, we might be inclined to “round up” or “round down” when reporting their beliefs to others. We might, that is, reframe their belief in binary terms. By way of illustration, suppose someone tells us that they are “somewhat confident” that abortion is morally impermissible. We might subsequently describe them as “believing that abortion is morally impermissible” or, more bluntly, as being in the “pro-life camp.” In doing this, though, we will be misrepresenting their beliefs. This “binary-belief bias” is unfortunate. What you believe matters, but how confident you are in the truth of a belief also matters. This is because your level of confidence will have an impact on whether and how you act on the basis of that belief, and if the belief that you are certain is true turns out to be mistaken, the consequences of acting on it can be disastrous, not only for you, but even more tragically for others who Is it ever appropriate to be absolutely certain of the truth of a belief? Yes, but only under special circumstances. We can, for example, be absolutely certain of the mathematical claim that 3 × 2 = 6. That claim is, after all, provable. We can likewise be certain of the truth of the logical claim that if a person is neither a golfer nor a bowler, then they aren’t a golfer. The same can be said of semantic claims, such as that there are no married bachelors. This is because bachelors are by definition unmarried. Allow me to ask a personal question: Are the people you believe to be your biological parents in fact your biological parents? You might feel certain that they are, but if you think carefully, you will realize that this feeling of certainty is unjustified. It could be that they are in fact adoptive parents who misled you about your origin, perhaps because they thought that doing so would be in your best interests. Alternatively, the people who raised you could sincerely believe that they are your biological parents, but there could have been a mix-up at the hospital. Such things happen! The takeaway from this is that, outside of special areas—including math, logic, and semantics—there is precious little about which a thoughtful person will be absolutely certain.* In general, your level of confidence in a claim should depend on the quantity and quality of the evidence that you have in support of it. A Thinker will realize as much. Consequently, if you ask whether they believe a claim, they might hesitate to give you a straight-out Yes or No answer, and might instead qualify their level of confidence: “Do I believe that the COVID pandemic resulted from a lab leak in China? There is a good chance that it did, but I am by no means certain.” Thinkers’ tendency to qualify their level of certainty with respect to a claim will, for many people, be a turn-off. Given a choice between a Thinker who believes that there is “a good chance” that COVID is the result of a lab leak, and a YouTube pundit who is absolutely certain that COVID is caused by cell phone towers, they will be drawn to the pundit. Would he, after all, be that certain if his beliefs were mistaken? By way of contrast, Thinkers will instinctively distrust those who (outside of the special areas we have discussed) feel certain of the truth of the claims they are making. Although evidence-based reasoning can justify our being quite confident that our conclusions are correct, it can’t justify absolute certainty. Although Thinkers will routinely qualify their level of confidence in a claim, they will typically be reluctant to quantify it. Suppose, for example, we ask whether they think a coin, when tossed, will come up heads. You might imagine that they would tell us that they are “50% confident” that it will, but this is unlikely. They will instead tell us that they are highly confident that there is a 50% chance that it will come up heads, which is an altogether different belief. And notice that they are unlikely to say that they are certain that there is a 50% chance, because they aren’t certain that the coin being tossed is fair. We have seen that Thinkers will have very many nonbeliefs. When they do believe something, though, they will attach a level of confidence to that belief. Furthermore, Thinkers are perfectly willing to change their level of confidence in a belief if they come into possession of new evidence, if they come to question the reliability of old evidence, or if they discover that the reasoning that led them from evidence to their conclusion was flawed. In an earlier post, I described a Thinker’s mindcleaning regimen. Its purpose is to find and “eradicate” their mistaken beliefs. In many cases, though, rather than eradicating a belief, a Thinker will adjust their level of confidence in it. They might also spend time and energy reassessing beliefs that they feel absolutely certain are true—again, outside of the special areas we have discussed. *Descartes famously declared that “I think, therefore I am.” In saying this, he was not saying that the activity of thinking gave his life meaning. He was instead explaining how he could be certain of his existence—more precisely, of the existence of his mind: By the very act of thinking, he provided himself with compelling evidence of his existence. Indeed, by the very act of doubting his existence—“Maybe I don’t exist…”—he also provided himself with compelling evidence of his existence. After all, a non-existent being couldn’t harbor such doubts. And to be clear, Descartes was not claiming that he could be certain of the existence of his body or even his brain. What he could be certain of (at least while he was thinking) was the existence of a “thinking thing,” namely, what we refer to as his mind. He also couldn’t be certain that other people have minds. That said, we would do well, in daily life, to assume that they do. Need more food for thought? Click here for my past essays, listed by title.