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Hello. I'm Joseph Wu, and I'm a Philosophy graduate student at the University of Cambridge. In this video, I'll be explaining the informal fallacy known as equivocation, a fallacy that comes up all the time. Before we look at some more problematic examples, let's start off with a simple one, to see how it works. Consider the following argument: Premise one: All stars are exploding balls of gas. Premise two: Miley Cyrus is a star. Conclusion: Therefore, Miley Cyrus is an exploding ball of gas. Wow, this is clearly a terrible argument! The form of this argument appears to be valid, and each of the premises, when considered individually, is true. You might recall from a previous video that an argument with a valid form and true premises is considered sound. You might also recall that a sound argument necessarily has a true conclusion. But you're probably not convinced that Miley Cyrus is an exploding ball of gas. And you're right to think that the logic is flawed. So what's wrong with this argument? This argument commits the fallacy of equivocation. Here, the word "star" is used with different meanings in the two premises. In the first premise, star is intended to mean something like: a celestial sphere of plasma. But then the meaning of star shifts in the second premise, where star refers to a famous person. The premises equivocate between two meanings of the word "star." To be precise, equivocation occurs when the same word is used to express different meanings through out an argument. The arguer is committing a fallacy, because he or she uses the word as if that word have the same meaning, and so the argument would appear to be valid, even though it actually is not. Equivocation results from ambiguities in language. Since many words can have more than one meaning, we need to be cautious that key terms are not shifting meaning during the course of an argument. Since equivocation results from multiple meanings of a single term, a helpful strategy to expose this fallacy is to restate the premises of the argument but without the ambiguous term. For example, let's substitute our definitions of the word "star" into the premises of the previous example. Premise one: All celestial spheres of plasma are exploding balls of gas. Premise two: Miley Cyrus is a famous person. Conclusion: Therefore, Miley Cyrus is an exploding ball of gas. Clearly, this argument isn't valid, once we got rid of the ambiguous term, "star." Even though both of the premises are true, the conclusion does not follow. This example is surely far fetched. After all, no one has ever equivocated Miley being a fomous person with Miley being an exploding ball of gas. But know that we understand how this fallacy generally works, let's look at two examples that are not so easy to spot. Suppose a respectable newspaper was criticized for spreading celebrity gossip., and suppose that, in response, the editor gave the following argument: Premise one: Newspapers have a duty to print stories that are in the public interest. Premise two: The public has great interest in rumors about celebrities, since circulation increases when newspapers print such stories. Conclusion: It's not wrong for respectable newspapers to pass on rumors about celebrities. As with our Miley Cyrus example, this argument appears to be valid. But is it actually? The key term that shows in both premises of this argument is "interest." So let's focus on how it is used. In the first premise, interest is used to mean the benefit of a person or a group, like in the sentence: It is in your interest to keep your bank account information private. In the second premise, interest is used to mean an activity one enjoys doing, like in the sentence: My interests are swimming, hiking, and reading. Since the meaning of the term "interest" has shifted between the first and second premises, this editor has committed the fallacy of equivocation; his argument isn't valid. Here's another example. Suppose your friend tells you this: Organic compounds contain carbon, and organic foods are better for the environment, so when you're grocery shopping, you should look for foods that contain carbon in it, as these foods are better for the environment. The absurdity of the conclusion should alert us that something has gone wrong int this argument. So let's take a closer look at how the term "organic" is being used. The statement "organic compounds contain carbon" is true. This is the scientific definition of "organic" used by chemists. The next statement:,"organic foods are better for the environment," is also true. But note that, now, the definition of organic refers to the methods by which that food was produced and processed. The term "organic" is now used in an agricultural sense, rather than a scientific one. This argument equivocates between two different meanings of organic, so it isn't valid. It's worth noting that even if we limit the term "organic" to its agricultural sense, the thread of equivocation still looms, due to the ambiguity of the term. For instance, different countries have different standards for what counts as organic. Different foods also adhere to different standards. And in the United States, there are various categories for labeling organic products, ranging from a product made with 100 % organic ingredients, to a product made with at least 70 % organic ingredients. If you're ever suspicious that an argument is guilty of equivocation, try the method we used in the first example of this video: First, distinguish the potential meanings of the ambiguous term in an argument. Then, restate the argument without the ambiguous term, so that the premises are still true. Finally, evaluate the translated argument. Is it valid? If not, then the argument has committed the fallacy of equivocation. Subtitles by the Amara.org community