 I don't know. It just started a new job. The apartment's a mess. Can I really justify doing thunk right now? Wait a second. What am I talking about? Just look at it. It is justified. The half dozen airports around London are dense with business travelers at just about any time of the year, and none are busier than Heathrow, the number two airport in the entire world. It's not unusual to suffer some sort of delay for one's flight because of traffic to or from the airport, or because someone's a little slow getting out of the terminal. When booking flights for big-wig executive types, secretaries might opt to send their bosses to one of the five airports around London that aren't Heathrow. Maybe save some cash or avoid traffic. But knowing all the drawbacks, all the chaos, and the likelihood of problems there, Heathrow is still the most popular option for business travel out of London. The problem is that Heathrow is viewed by most people as the default option, one which can be justified easily. A secretary who sends someone out of some other airport will inevitably get interrogated for any issues that might arise, even if, statistically speaking, getting stuck in traffic or being delayed is less likely. If anything does go wrong, they will be asked to justify their decision, and if they can't supply a decent justification for making that choice, they will be held accountable for the outcome. It's a much, much safer play to sign someone up for the slog out to Heathrow, so that's exactly what happens, again and again. The Heathrow option is a lovely euphemism for decisions which are easily justified, but not necessarily rational, that is, not aligned with the most desirable outcome. We usually think of those terms as being too facets of the same thing. If a belief is rational, then it's justified. Having a justification for what you're doing means that you're acting rationally. There are ways of looking at the situation and saying, well, the decision isn't really justified, or well, it's technically rational, but we can feel the two being teased apart in some sense. It's not an uncommon thing. In game theory, there's a whole class of cases like the Heathrow option called paradoxes of rationality, where the most justified course of action invariably results in worse outcomes. That's kind of weird if you think about it. I mean, the whole point of formal analytic tools like logic and argumentation is to justify our assertions, which is supposed to ensure that our conclusions are rational. Take the classic logical syllogism. Socrates is a man, all men are mortal, therefore Socrates is mortal. It's a deductive proof showing how to justifiably navigate from a set of known premises to a rational conclusion. Or does it? Looking closely, you might notice something peculiar about the second premise. All men are mortal. How exactly do we know that that's true? Well, we could use induction, generalizing from a few men who turned out to be mortal to all men, but there are some uncomfortable problems with induction, as we've discussed on THUNK. You might have heard that correlation doesn't imply causation, but that's all that induction is, assuming that it does. The number of federal dollars spent on science and tech correlates very closely to deaths by strangling and suffocation. So, inductively speaking, we should expect a sudden increase in NASA funding to cause a sudden spike in garottings. But we don't, because that's crazy. Yet we do expect one more man to result in one more mortal, even though the only evidence we have is that when we see one, we see the other. But hey, this syllogism is pretty simple, so let's just do this deductively. Ignoring the logistics for a moment, if we're being really thorough and making sure that we've got a truly watertight deductive argument, we'd simply have to go through and verify that for every member of the set of men, each member truly is mortal. But that set includes Socrates. To accept this premise, it seems that we'd have to verify that Socrates is mortal, which is what we're supposedly proving in the first place. If you're familiar with logical fallacies, you might notice a whiff of something like begging the question, a logical misstep where someone assumes the thing they're trying to deduce. Like, the prime directive is important, Picard is the best captain in Star Trek, therefore Picard is the best captain in Star Trek. It doesn't actually demonstrate anything we didn't agree with already, we're not getting anything more out of it than we're feeding into it. Some philosophers think this question-begging thing is endemic to all logic, that if you're doing a logical proof, you're intrinsically begging the question and assuming the conclusion that you wanted to demonstrate. That's a real problem if you want to, say, prove anything with logic. It seems that we're in a bit of a bind here. On one hand, we've got a problem with proof by induction. On the other hand, we've got a problem with proof by deduction. As Mary Berry might say, we're just a touch under-proofed. It seems that we've disqualified all methods of normative justification in this chain of reasoning, so we don't have any good reason to believe it. There are a couple of directions we might go from here. Philosophical irrationalists assert that the dictates of reason tell us that we should reject reason itself as a basis for truth, and I hate to say it, but these sorts of observations might well push one in that direction. If justification doesn't have any place in reasoning, you can just choose to believe or act however you like, and if you want, use reason to feel good about it afterward. As David Hume put it, reason is an ought only to be the slave of the passions and can never pretend to any other office than to serve and obey them. But there is another option. Karl Popper is most well-known for his philosophy of science, specifically the demarcation problem of how we can know science from non-science. He asserted that one of the things that you absolutely need to call a theory scientific is a criterion of falsification. Some observation are finding that would imprintable prove that the theory was incorrect. Popper found this business about justification reason fascinating, but rather than following Hume into irrationalism, he found a way to rescue a normative sort of rationalism from the problems we've examined, in a familiar way. Popper's theory of critical rationalism accepts these critiques of justification's role in reasoning head-on. Justification is a masturbatory exercise to feel better about decisions and beliefs we already hold. If you want something to be true, you can always gather evidence to believe it or prove it logically without too much trouble, so justification is simply bankrupt as a foundation for knowledge. But what about criticism? What about things that reason tells us can't be true? The distinction might seem subtle, but it makes a world of difference when we're talking about how we might use reason to know things. As with Popper's scientific demarcation, according to critical rationalism, when we're reasoning properly, we're guessing what might be true, then subjecting that guess to various tests of consistency in comparison with evidence. Not to see if we can justify it, but to see if there's anything that disqualifies it from the realm of potentially rational notions. That puts objective truth much further out of reach that we generally like to think that it is. Without the option of confirmation, all we have left is a set of ideas that we happen to come up with, which are internally consistent and aren't explicitly contradicted by any of the criticism or evidence we've raised so far. That's a pretty small needle to thread, and if we're limited in some important way in what sort of guesses we can make in the first place, either because our puny human brains can't even come up with the right sort of ideas or because we can't recognize them as being worth reasoning about, it's possible that we simply can't get close to the truth. But importantly, this still allows room for reasoning as a normative process, something that can, in principle, distinguish between irrational and potentially rational beliefs and behaviors. By eliminating justification as a mechanism of rationality, it undercuts a lot of stuff we normally associate with reasoning, the sort of prescriptive approach of proving that the rational thing to believe or do is this, that, or the other. That sort of thing remains in Hume's irrationalist camp, a frivolous bit of rhetorical posturing. But by abandoning justification, it allows us to focus on the meaningful work of criticism, poking holes in ideas, finding inconsistencies or counterfactual evidence to prune away the bits that we can be sure are wrong. The ideas that seem especially useful and resilient against criticism, while still making substantive claims, are probably closer to being right. We can't ever really know for sure, but we can compare notes and get better guesses than we would on our own. The resemblance between critical rationalism and Popper's theory of demarcation is striking. By focusing on disproving things that aren't true, rather than proving things that are, he builds a convincingly robust account of how these tools can continue working, even under highly persnickety philosophical scrutiny. It's fascinating that he establishes such a relationship between reason and scientific investigation. Maybe even helping to explain some part of the fruitfulness of scientific methods. Skeptically-minded philosophers find Popper's defense of reason insufficient to rescue it from relativist or postmodern arguments, saying that even his deflated account of reason's role in objective truth overstates what it can reliably do. More positively-minded philosophers find his defense lackluster, suggesting it's defeatist to abandon induction entirely. Of course, Popper would probably have welcomed these critiques of his theory. But what do you think of his anti-justificationist position of critical rationalism? Please leave a comment below and let me know what you think. Thank you very much for watching. Quick plug, the Discord server is phenomenal. I have a link down in the video description. Please, please, please come and say hi and chat with some of the remarkable people there. They're very interesting to talk to. And don't forget to blah, blah, subscribe, blah, share. And don't stop thunking.