Phil 157 Fall 2023 Moral Issues R. Kumar Arguments WHAT'S AN ARGUMENT? · An argument is a set of claims, one of which, the conclusion, is supported by the others, the premises. The aim of an argument is to provide reasons in support of a certain claim. A good philosophy paper is a paper in which a powerful argument is offered for a certain claim. The aim is to persuade the audience of its conclusion by supporting it with plausible premises. An example of an argument: A fetus is a person. Killing a person is always wrong. Therefore, abortion is always wrong. Sometimes the structure of an argument is less obvious: Because euthanasia is murder, it is always morally wrong. The structure of this argument, made fully explicit, is: 1. Euthanasia is a form of murder. 2. Murder is always morally wrong. 3. Therefore, euthanasia is always morally wrong. Common premise-indicators: because, given that, since, for. Common conclusion-indicators: therefore, so, hence, thus, it follows that, consequently. VALIDITY: . An argument is valid if the conclusion logically follows from the premises: if it is the case that, were all the premises to be true, the conclusion couldn't fail to be true. Example of a valid argument: 1. All cats are reptiles. 2. Bugs Bunny is a cat. 3. Therefore, Bugs Bunny is a reptile. This argument is valid because, if it were the case that all the premises were true, then the conclusion would be true. Notice that the conclusion of a valid argument can be false, as long as some of its premises are false. When an argument is valid, any argument of the same form is valid: All As are Bs. X is an A. Therefore, X is a B. 1
Example of an invalid argument: 1. If a person is Prime Minister of Canada, then they identify as male. 2. Justin Trudeau identifies as male. 3. Therefore, Justin Trudeau is Prime Minister of Canada Notice that an invalid argument can have a true conclusion. In order to unmask an invalid argument, it is helpful to look for an argument with the same form that has true premises and a false conclusion: If P, then Q If a person is Prime Minister of Canada, then they identify as male Q Elon Musk identifies as male Therefore, Elon Musk is Prime Minister of Canada Therefore, P If, given an argument, it is possible to find an argument with the same form that has true premises and false conclusion, then the original argument is invalid. Note: Sometimes authors leave some of their premises implicit. If so, the argument will be invalid until we make them explicit. We must do this in order to interpret them charitably. SOUNDNESS: · An argument is sound if it is valid and its premises are true. Notice that any sound argument must have a true conclusion. This is the type of argument philosophers aim for. Example: All persons are mammals. I am a person. Therefore, I