Do you exist?
“What? Of course I exist. What a stupid question.”
Okay, now that I’ve proven that I have psychic powers by predicting your answer ahead of time (You believe me, right?), take a step back from the question. How do you know that you really exist? It is, after all, possible that you are nothing but a Matrix-style AI simulation of consciousness being studied by a highly advanced future society. Can you prove that you’re not? It’s entirely conceivable that a society could develop the technology necessary to simulate reality—it’s not even that much of a stretch to suggest that we may be able to do this within our lifetimes (combine modern video games with Japan’s Earth Simulator, then extrapolate). Once you’ve accepted that, how can you know for sure that you’re not an AI operating within a highly advanced reality simulator? Granting that such a thing is theoretically possible, you really can’t. If you can’t entertain the mere possibility, however, I have bad news for you: you’re suffering from a chronic mental illness called certainty.
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Why do we think we know anything in the first place? It’s a product of our operating under the fundamental assumption that reality is consistent. We do this because our observations seem to favor this hypothesis. The sun “rises” every day. Our bodies get hungry if we don’t eat. Trees don’t get up and walk around (as least not while being observed!). These facts of life are so reliable that we take them for granted. I have never fallen up into the sky, so I conclude that I will not suddenly find myself sucking vacuum tomorrow. It is, of course, possible that a freak accident will occur at some point, propelling me ever upwards beyond the Earth’s atmosphere, but I lose no sleep over this possibility. It simply is not a concern. Why not? Because I conclude, just as you do, that the probability of this happening is low enough not to merit any serious consideration. Similarly, do you find yourself often worrying that you will fall through the ground and found yourself trapped in the Earth’s crust? Probably not, but there still exists a possibility, however slim, that an earthquake tomorrow will lead you into just this circumstance.
Why is any of this relevant? No matter how hard we try, there can be no absolute certainty about external reality (that is, about the world that exists outside of your immediate consciousness). That’s important, so hold on to the idea for a moment. I am comfortable claiming to be certain that I will not spend tomorrow night in orbit around the Earth, but is this absolute certainty? No, this is simply an artifact of probabilistic rounding. Because this has never happened to anyone in recorded history, I consider the possibility of it happening to me to be sufficiently near 0% to discount it entirely. The infinitesimal likelihood of it happening, combined with a lack of evidence that this state will change (like the development of an antigravity gun), means that we can take it for granted that this simply will not happen. In making this claim of certainty, however, we risk making a kind of equivocation. Ultimately, the only interpretation of certainty that has any place in rational discourse is the one that means “overwhelmingly likely,” and anyone who tries to argue that they have “absolute knowledge” has exempted themselves from being taken seriously.
That’s why it bothers me when someone confesses an absolute belief in anything. All knowledge is inherently conditional. In math class, we’re initially taught to divide and consider something called the remainder before being taught about fractions and decimals. This is an incomplete model, but we accept it temporarily, until a more accurate model is introduced. So too with all knowledge. We refine our understanding of the world as we gain new knowledge. Every now and then, we uncover a truth that causes us to rewrite what had been seen as comprehensive theories. The medieval church was quick to condemn Galileo for challenging the convention that the Sun revolved around the Earth, but evidence has since come to light proving the geocentric model of astronomy terribly wrong. For as strongly as the church believed that the Earth was the center of the universe, their beliefs were contradicted by reality, and they were forced to adopt the new model. Even if the pope had, with absolute certainty, engraved into stone tablets that we were at the center of it all, that would not have made it so.
Thus, when I hear someone profess to know with absolute certainty that God exists, I want to throw up a little. Any such profession of Ultimate Truth™ is the strongest possible example of the human mind’s propensity for self-deception. The Bible serves as True Evidence™ of God just as much as the Napkin serves as True Evidence™ of the Napkin Religion; no matter how strong your faith, you cannot reasonably state that you have absolute certainty of its truth.
This seems to come up pretty often when certain types of religious people (the Ray Comforts and Eric Hovinds of the world) try to engage in serious conversations with scientists (or even moderately educated laypeople). I get especially perturbed when someone suggests that admitting a lack of absolute certainty is somehow equivalent to confessing a complete lack of knowledge. The believer ends up making a claim along the lines of “You admit you don’t know for sure, but I have absolute certainty because God said so.” In this case, the believer is lying to themselves. These people aren’t interested in the honest pursuit of knowledge; they want to sell you something, and the price is always too high.
To be intellectually honest, we can never claim 100% certainty about objective reality. (For example, “God exists” is indefensible while “I believe God exists” can be safely professed.) When we say that we cannot be absolutely sure that a given theory is accurate, this is not a weakness in the model! Rather, it is instead an attempt to be intellectually honest; it is possible that another Galileo will come along to demonstrate that our present hypotheses are incorrect, but the nature of scientific inquiry makes this progressively less likely as additional evidence mounts. In essence, any time a scientist says “we know that X is true,” what this really means is “we have a significant predominance of evidence in support of the hypothesis that X is true.” We only resort to substituting “we know X” as an attempt to save time. In the scientific world, it is taken for granted that hypotheses, theories, and even laws are contingent upon evidence. It is possible that the germ theory of disease will be disproven some day, but the likelihood of this happening is so close to 0 as to be completely discounted.
We may not be able to disprove the Reality-is-the-Matrix hypothesis, but that alone does not mean that it subsequently stands at equal footing with the Reality-is-Reality hypothesis. Are we living in a Matrix? Probably not, but maybe. (There’s no evidence to support the idea that we are, so why worry about it?) Science is a process of gathering knowledge about the world, and one of its most important lessons is that absolute certainty is a mental disease that halts further understanding. Once we presume to know all there is to know about something, there is no reason to continue studying it. Learning stops. Thus, not only is absolute certainty an illusion, it’s also actively harmful. By falling into this trap, one closes the door to considering other alternatives. It renders one immune to reason and evidence. It is a delusion.
At its core, absolute certainty is a way of shielding oneself from the terror of not knowing. The cosmos is incomprehensibly complex, and we possess only the tiniest shreds of knowledge about it. Clinging to this false notion of certainty is nothing more than a coping mechanism to endure the overwhelming mystery of it all, yet it is maladaptive because it limits our ability to discover real truths. An unanswered question does not necessarily need to be daunting. We do not need to pretend to have all the answers; indeed, to have any hope of coming closer to this goal, one must discard the notion of certainty. The fullness of reality is far more complex and wonderful than the muddled depictions of any holy book. We have the potential to appreciate the unknown—to regard it as a challenge. Embrace that challenge by rejecting claims of absolute certainty, and recognize that doing so is the first step on the path to knowledge.