Welcome to week ten of our course. In this week, we'll be studying fallacies of relevance and vacuity. Now, before I say what fallacies of relevance and vacuity are, let me make an important distinction between the fallacies of relevance and vacuity that we will be studying this week. And the fallacies of vagueness and ambiguity that we studied last week. The important distinction that I have in mind is this. Fallacies of vagueness and ambiguity are very hard to avoid, whereas fallacies of relevance vacuity are quite easy to avoid once you recognize what they are. The reason that fallacies of vagueness and ambiguity are very hard to avoid, is because it's very easy to make those fallacies given the pervasiveness of vagueness and ambiguity in the language that we speak. Now you might think well, but why should there be vagueness and ambiguity in the language that we speak? I mean, why don't we just speak a language that does away with vagueness and ambiguity. In fact there are a lot of communities that tried to purge their technical language of vagueness and ambiguity. Like in scientific communities, they might try to use a language that doesn't have the same amount of vagueness and ambiguity that we have in ordinary language. But why don't we purge vagueness and ambiguity from ordinary language? Is it just a bother to purge ordinary language of vagueness and ambiguity and that's why we don't do it? Well, now, I think there's actually a deeper reason. I think there's a reason why it's important for ordinary language to have vagueness and ambiguity in it. And as long as ordinary language does have vagueness and ambiguity in it, it's going to, it's going to be very hard for us to get rid of fallacies of vagueness and ambiguity. We can do it, but we have to keep a watchful eye out for cases where we're using phrases that are ambiguous or vague in our arguments. Okay, so why is it important for ordinary language to have expressions that are vague or ambiguous? Well, let me give you some examples. Suppose we're planning a vacation, and we're planning a vacation to an island in the Caribbean. Let's say Jamaica and we're trying to figure out when the best time would be to go. And we think well, we don't want to go in the summertime because it will be too hot there. We want to go in the wintertime because then we get maximum relief from the cold that we experience where we live right now. So, let's say we decide okay, we want to go to Jamaica in the wintertime. Okay, fine. In the wintertime. but when in the winter time is the best time to go? Well, it's going to depend on a number of things. It's going to depend on exactly when the kids have vacation from school. It's going to depend on exactly when our workload is going to be the lightest at work. it's going to depend on when we save up the money for the vacation. So we have to think about when would be the best time in the winter time to go. But if you ask us, do we have any plans for travel? Well, we could say, yeah, we plan to go to Jamaica this winter. Well, when this Winter, you might want to know. December 24th or December 28th or December 31st? When? Well, we might say, we don't know exactly when, but sometime this winter. Okay, now, our answer to you is vague, where it's sometime this winter. Not clear exactly when. Well, you might say, okay, but even that could be made precise. You could say, well, we planned to travel to Jamaica between the following dates, December 21st and March 21st. Well, but our plans aren't even that precise, because maybe when we look at all the availability, it'll turn out that March 22nd is the best day to go. Or maybe March 23rd, or maybe December 20th. Right, so we can't even make our plans as precise as all that. So, if we're going to answer your question, we have to give you a vague answer. We can't give you a precise answer. We could try to give you a precise answer in probabilistic terms. We could say well, there's a high probability that we'll go in January or February. There's a lower probability that we'll go in December or March, and there's a very low probability that we'll go in early December or late March. But wait a second, even there our answer wasn't precise. We were talking about a high probability, a lower probability. What exactly counts as a high probability? Is it a probability greater than 50%? So it's hard for us to answer your question with any precision. So if we can't answer you question with any precision should we just remain completely uninformative. And when you ask, do we have any plans for travel, we should just say we don't know. Well that seems unhelpful. It seems much more helpful to give you a vague answer, yeah, we're planning to go to Jamaica some time this winter. That's much more helpful than giving you a response of the form, we don't know. Or of course, we could just make up a precise answer, and say, yes, we plan to go to Jamaica on December 28th. But then we'd be lying, because we have no idea whether or not we plan to go to Jamaica on December 28th. Or if not lying, in any case, we'd be saying something that we haven't the foggiest idea wheter or not it's true. So, in order for us to answer your question helpfully, we have to give a vague answer. And that's just one example out of many I could have produced, of a case where in order to be conversationally cooperative, we have to say something vague. So vagueness is important to ordinary language. So is ambiguity because one of the ways that we generate ambiguity is through metaphor and through figurative language generally. If I say, the White House said today that the conflict in Afghanistan is expected to decrease over the next 12 months Well, you might say, what do I mean the White House said? Does the White House have any organ that allows it to speak? No. The White House is just a building. Buildings can't speak. Well sure, you could say buildings can't speak, but when I say the White House said I meant a particular office said. Oh wait, you might object. An office said? What do you mean? A room with walls and a ceiling said something? Well, no. A room with walls and a ceiling didn't say something. But a particular person or group of people who work in that room with walls and a ceiling said something. Oh, which people were those? Well, I don't know. I don't know if it was President Obama who said it or if it was his White House Press spokesperson, or if it was some other member of the administration. But I don't need to know, in order to answer your question helpfully, when I say the White House said it. There, I'm using the phrase, the White House in a different sense than it's literally intended, right, the literal meaning of the White House is to refer to a particular building. Now, I'm using the phrase the White House to refer to a particular group of people who said something, but I can't be any more specific than that. I don't know which among those people said it, so I just say the White House said it. Okay, so these are examples of how vagueness and ambiguity are actually useful. To ordinary language. They're useful to the language that we speak in day-to-day life. So we can't get rid of them, and we shouldn't get rid of them. They're useful. But the problem is, as long as they exist in ordinary language, it's going to be very easy to make fallacies of vagueness and ambiguity. And so we're going to have to look out for such fallacies when they occur. Now with the fallacies that we'll be talking about this week, fallacies of relevance and vacuity, they are not like that. Fallacies of relevance and vacuity. Are much easier to root out once we know that they are. There's nothing about our ordinary language that tempts us into making fallacies of relevance and vacuity. Once we've identified what they are, we should be able to eliminate them. So, what are fallacies of relevance and vacuity? Well, I'll start out today by giving you some definitions, and then in subsequent lectures, we'll talk about particular examples. So, fallacies of relevance and vacuity. First, what's a fallacy of relevance? A fallacy of relevance is, is a fallacy that results when an argument's premises are not relevant at all to supporting its conclusion. Now, examples of these sort of fallacies are what we are going to call ad hominem arguments. Appeals to authority, and appeals to popular opinion, and we are going to be discussing all of those in subsequent lectures. What's an example of a fallacy of acuity? Well, first let me give you a definition. A fallacy of vacuity is a fallacy that results when you can't be justified in accepting the premises of an argument unless you're already independently justified in accepting the conclusion. So, in other words, even if the argument is sound, the premises can't give you a good reason for accepting the conclusion. Because you already have to have a good reason for accepting the conclusion in order to accept the premises in the first place. And examples of those are what we're going to call circularity, begging the question, and self-sealing. And again, in subsequent lectures, we'll look at examples of all of those. Okay, see you next time.