If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:3:05

Video transcript

(intro music) Hi, I'm Kelley Schiffman. I'm a PHD student at Yale University, and today I'd like to talk[br]about suppressed premises. So, very often when we present an argument for a conclusion, we[br]don't explicitly state all the premises required for[br]getting to the conclusion. Consider this example: Premise (1): Mike is a Canadian. Conclusion: Mike must be polite. To get from the premise[br]that Mike is a Canadian to the conclusion[br]that Mike is polite, we need a second premise saying that all Canadians are polite. Only then is this argument strictly valid. Only then does the conclusion follow from the premises. Now, premise two here, the premise that all Canadians are polite, is an example of what we[br]call a "suppressed premise." Consider this other example. Premise (1): Smoking[br]will damage your health. Conclusion: So, you shouldn't do it. Here, the suppressed premise is the claim that you shouldn't do things[br]that damage your health. Now, notice that in both of these cases, even though these suppressed premises are required for the argument to be valid, it seems nonetheless acceptable to leave them only implicit, to not state them explicitly. But why is this? I would suggest the following: that it's okay to keep[br]a premise suppressed if two conditions are met. First, that the premise[br]is uncontroversial. And second, that it's[br]obvious to the person being presented with the argument. If both of these conditions are met, then it seems acceptable to[br]keep the premise suppressed. Sometimes, however, a premise[br]will be left implicit, it will be left suppressed,[br]even if it fails to meet these conditions. Now, sometimes this is[br]done unintentionally. Other times it's done in order to make the argument appear more persuasive than it really is. Regardless, that's why it's important to be sensitive to the possibility of suppressed premises, and to develop a habit[br]for identifying them. Consider the following argument. Premise (1): Killing an[br]innocent person is wrong. Conclusion: Therefore, abortion is wrong. The suppressed premise[br]here is something like "To have an abortion is to[br]kill an innocent person." That's the suppressed premise. Now, regardless of whether this premise is true or false, it certainly[br]isn't uncontroversial. It doesn't meet condition one. Nor can one count on others taking this premise to be obvious. It doesn't meet condition two. It's therefore a premise[br]that should be made explicit and critically reflected upon when assessing the[br]strength of the argument. It's in cases like this where sensitivity to suppressed premises is truly important. Subtitles by the Amara.org community