Here are some claims which make up an argument, or would make up an argument if they were given in a more logical order. Exercise: figure out which of the following claims is the conclusion of the argument (the others are the premises).

(1) (a) There is a problem with your transmission.

(2) (a) Abortion is wrong.

The arguments in the readings will usually not be given in this compressed, "schematic" form. Rather, you will have to extract premises and conclusions from much more complex and lengthy passages of text. In doing this, it is helpful to look out for certain key words which often serve as indicators of ("flags" for) premises or conclusions.

Some common premise-indicators are because, since, given that, for. These words usually come right before the claim which is the premise. Examples of the use of such "flags" for premises:

Some common conclusion-indicators are thus, therefore, hence, it follows that, so, consequently. These words usually come right before the claim which is the conclusion of the argument. Examples of the use of such "'flags" for conclusions:

It is also helpful to use these premise- and conclusion-indicators in your own writing, to make the structure of your arguments clearer. Don't use them lightly, however: make sure they really are "flagging" either a premise or a conclusion of your argument, as appropriate. Anyone reading your paper is entitled to think that claims preceded by because, &c., are premises, and that claims preceded by therefore, &c., are conclusions. Make sure they are, or you are misleading the reader.

Definitions:

Note that there are perfect good arguments that are nonetheless not valid ("invalid"). For example:

However, the arguments that we will encounter in this course will be any good only if they are valid. So, the first thing you should ask yourself in evaluating an argument from the readings-or one of your own-is whether it is valid. Does the truth of the premises guarantee the truth of the conclusion? Is it possible for the conclusion to be false, if the premises are all true? Exercise: determine, for each of the following arguments, whether it is valid or invalid. If invalid, explain why.

(5) If the moon is made of green cheese, then cows jump over it.

(6) All engineers enjoy ballet.

Therefore, some males enjoy ballet.

(7) Abortion is morally wrong.

Sometimes an argument which is invalid as written can easily be "fixed up" so that it is valid and in line with what the proponent of the argument intended. The most common reason for this kind of "corrigible," invalidity is missing premises. Sometimes a writer does not state all of his or her premises explicitly, and this renders his or her argument invalid. In such cases we can make the argument valid by supplying an appropriate premise, supposing that the writer intended it to be a premise all along. You should become adept at filling in missing premises so that you can see the structure of an argument more clearly. Exercise: supply the missing premises to arguments (6) and (7) above, and to the following arguments:

(9) Abortion involves terminating the existence of some organic matter.

Therefore, abortion is always morally wrong.

Note that sometimes a premise is left out because it is taken to be obvious, as in arguments (6) and (8) above. However, sometimes the missing premise is contentious, as in (7) above. Sometimes, in fact, it is the most contentious premise of the argument, as in (9) above.

Definition:

Argument (5) above is an example of a valid argument which is not sound ("unsound").

Note the following fact, which is a consequence of the definitions of soundness and validity:

(11) The conclusion of a sound argument is true.

This fact has practical import. It means that if you read someone's article and disagree with his or her conclusion, the onus is on you to show why his or her argument is unsound. For (by (11)) if it were sound, the conclusion would be true. Therefore, if (according to you) the conclusion is false, the argument must be unsound. This means that either the conclusion does not actually follow from the premises-in other words, there is a problem with the author's reasoning or logic-or at least one of the premises is false. In this subject, it is never enough simply to say that you disagree with someone's position, or that their position is wrong. If it is wrong, there must be something wrong with their argument, and you need to say what it is.

Soundness is thus the most important criterion in evaluating both arguments from the readings and your own arguments. After having identified the conclusion for which a writer is arguing, and the premises which he or she advances in support of that conclusion, you should attempt to determine whether the argument, thus reconstructed, is sound. And in making arguments of your own, you should always try to give a valid argument the premises of which are true, or at least defensible.

Here are some examples of valid forms of argument.

Modus ponens. The general form of a modus ponens argument is given in (1). Two examples follow.

Modus tollens. The general form of a modus tollens, argument is given in (4). Two examples follow.

(5) If Boston is balmy then Caracas is chilly.

Disjunctive syllogism. The general form of a disjunctive syllogism is given in (7). Two examples follow.

(7) (Either) P or Q. (Either) P or Q.

Not-P. --or-- Not-Q.

Therefore Q Therefore P.

(8) Either Colonel Mustard or Miss Scarlet is the culprit.

Categorical syllogism. Two general types of categorical syllogism are given in (9). Two examples follow.

(9) All Fs are G . All Fs are G.

x is (an) F. --or-- All Gs are H.

Therefore x is G. Therefore all Fs are H.

(10) All men are mortal.

Here are some things which make an argument a bad argument.

The fallacy of equivocation using key terms in different senses in different parts of the argument.

Begging the question (also known as a circular argument): assuming what you are trying to prove. We will seldom see really obvious cases of begging the question in the readings. What we may see is a weak form of begging the question, namely putting forward as a premise something so close to the conclusion that no one would believe the premise who didn't already believe the conclusion. An ineffective mode of argument, precisely because it does not persuade.

Proving too much: an argument is said to prove too much if it appeals to a principle which has consequences that the formulator of the argument would not accept, or which are clearly erroneous. Example: Abortion is wrong because it kills something that is living. This proves to much, because it would imply that it is wrong to pull up weeds.

Ad hominem arguments: an ad hominem. argument involves a personal attack on one's opponent rather than a reasoned objection to his or her position or argument. A variant concludes that a position is wrong because of the people who hold it. Examples: Hitler enjoyed Wagner, therefore Wagner is evil. Senator X has argued that the minimum wage ought to be raised, but Senator X is well known as an adulterer.

Appeals to authority : in philosophy, there are no authorities. It is never acceptable to support a position simply by pointing out that someone we've read holds it. You can explain why you think Professor X's arguments for that position are persuasive, but a mere statement that the renowned Professor X holds a certain position carries no argumentative weight. Appealing to supposed authorities in this way is the mirror image of an ad hominem argument. Example: According to Professor X, abortion is morally permissible even if a fetus does have a right to life. Clearly, then, there can be no moral objection to abortion.

Straw man arguments: representing your opponent's position or argument unfairly so that it is easier to shoot down. In such cases, all you have shot down is a It/ straw man," not your actual opponent. Example: Those who oppose affirmative action think that white males should have a monopoly on all jobs, money, power, and success in society. I will show that this position is morally repugnant and contrary to democratic principles, hence affirmative action is justified.