Understanding Arguments: Logic, Premises, Conclusions, and Truth - Prof. Mikhail Valdman, Study notes of Introduction to Philosophy

Download Understanding Arguments: Logic, Premises, Conclusions, and Truth - Prof. Mikhail Valdman and more Study notes Introduction to Philosophy in PDF only on Docsity! Excepts from S. Morris Engel’s With Good Reason 2. LOGIC AS THE STUDY OF ARGUMENT Logic is the study of argument. As used in this sense, the word means not a quarrel (as when we "get into an argument") but a piece of reasoning in which one or more statements are offered as support for some other statement. The statement being supported is the conclusion of the argument. The reasons given in support of the conclusion are called premises. We may say, "This is so (conclusion) because that is so (premise)." Or, "This is so and this is so (premises); therefore that is so ,'(conclusion)." Premises are generally preceded by such words as because, for, since, on the ground that, in as much as, and the like. Conclusions, on the other hand, are generally preceded by such words as therefore, hence, consequently, it follows that, thus, so, we may infer that, and we may conclude that. The first step toward understanding arguments, therefore, is learning to identify premises and conclusions. To do so, look for the indicator words, as they are called, just listed. In arguments where such indicator words are absent, try to find the conclusion by determining what is the main thrust of the argument: the point' the argument is trying to establish. That will be its conclusion; the rest its supporting grounds or premises. Distinguishing the conclusion from the premise or premises in the following two arguments is easy, for in the first case one of its statements is preceded by the word for (which tells us that what follows is a premise and what remains must be its conclusion) and in the second, one of its statements is preceded by the word hence (which tells us that what follows is a conclusion and what remains must be its premise): a) Jones will not do well in this course, for he is having a hard time concentrating on schoolwork this semester and has hardly attended any classes. b) She has antagonized nearly everyone in the office; hence it is unlikely that she will be granted the promotion. In the following two examples, however, no such helpful indicator words are present: c) There are no foxes in this area. We haven't seen one all day. d) All conservatives opppose public housing; Senator Smith opposes it; he must be a conservative. To distinguish the premise from the conclusion in cases of this sort, ask yourself such questions as: what is being argued for and what is the person trying to persuade us of? In case c what is being argued for is not that "we haven't seen a fox all day"-for the other person obviously already knows this and is simply being reminded of it-but rather that, in light of this known fact, there must be no foxes in this area. That is the conclusion of the argument. Similarly with example d: what is being argued for is not that "all conservatives oppose public housing," nor that "Senator Smith opposes i t"-for in this argument these are assumed to be shared statements of fact and stated as such-but rather that, in the light of these facts, Smith must be a conservative. Finding the conclusion in an argument where it is not clearly indicated as such will not always be easy or certain. Our best aid will be attending carefully to the content and tone of the argument and to the direction of its reasoning. · An argument is a piece of reasoning in which one or more statements are offered as support for some other statement. · The statement being supported is called the conclusion of the argument; the reasons given in support of it are called the premises. · Indicator words such as since, because, and for generally precede premises; words such as therefore, hence, and consequently precede conclusions. · In arguments where such indicator words are absent, try to find the conclusion by determining the point the argument is trying to establish. That will be its conclusion; the rest will be its supporting grounds or premises. 3. ARGUMENTS AND NONARGUMENTS As we have seen, an argument is a piece of reasoning in which one or more statements are offered as support for some other statement. If a piece of writing makes a claim, but gives no such reasons for us to believe it, it is not an argument. Likewise, a passage that makes no assertion at all is not an argument. Thus questions are not arguments, nor are announcements, complaints, compliments, or apologies. Such passages are not arguments because, again, they make no effort to persuade us. For example, "Are there any plans to put `The Little Rascals' on the air again?" is merely a question, not an argument. It requests information, not assent to some claim. The same is true of the following examples: a) I'm not going to watch anymore TV programs with laugh tracks. There's laughter if someone shuts a door. I'll laugh when I want to laugh. I think they should put the laugh tracks on the evening news when the weather forecasters are on the air. b) I spent $125 to attend a reincarnation seminar and the leader appeared in a racing jacket, jeans, and a T-shirt advertising a California guitar shop. I consider that bad taste in Philadelphia. He is certainly the best' regressionist I've seen in my sixty years, but you can have his Kung-Fu approach to spirituality. c) The sincerest satisfaction in life comes in doing and not in dodging duty; in meeting and solving problems, in facing facts, in being a dependable person. Example a is an expression of contempt and disgust, b is a complaint, and c merely a statement of a point of view without any attempt either to argue or persuade us of it. On some occasions the conclusion of such an argument may accidentally happen to be true, as in: c) All cats are animals. All tigers are animals. Therefore all tigers are cats. In such a case we cannot determine the truth of the conclusion from the argument itself; the conclusion may be true but not for the grounds offered in defense of it in this argument. 3. We may have our facts wrong (one or more of our premises is false), but we may make proper use of them (reason validly with them). In this case, our argument will be valid but unsound. d) All movie stars live in Hollywood. Robert Redford is a movie star. Therefore Robert Redford lives in Hollywood. Here the first statement is clearly false, yet the reasoning is valid and the conclusion follows from the premises. As in case 2 above, the conclusion may happen to be true but we cannot determine its truth within the terms of the argu- ment. It might be true despite the falsity of the first premise; on the other hand, it might be false despite the validity of the reasoning. In order to reach a conclusion that we can depend on to be true, it is not enough to reason validly; we must do so from true premises. 4. There is, finally, the case in which our facts are wrong (one or more of our premises is false) and we also make improper use of them (reason invalidly from them). In such a case the argument will be both invalid and unsound. e) I like this course. All final examinations are easy. Therefore I will receive a high grade in this course. Since only one of the argument types we have discussed can yield conclusions that must be true, the reader may wonder why we should be interested in arguments whose premises are false. For better or worse, we are sometimes in a position where we do not know whether our premises are true. Being able to infer validly the consequences which would flow from such premises if they were true enables us to judge whether they are true. For if, by a deductively valid inference, we should arrive at a conclusion that we know is false, then we can be sure that at least one of our premises is false, because a false conclusion cannot validly be deduced from true premises. An interesting example from the history of science concerns the formerly held corpuscular theory of light. This theory maintained that particles of light must travel in straight lines through empty space, but it eventually was realized that if this theory were true, then light particles traveling through a circular hole in an opaque shield would project a sharply defined circle of light onto a screen behind the shield. In a subsequent experiment using a very tiny hole, however, the image projected on the screen was not a sharply defined circle of light at all, but rather consisted of concentric alternating light and dark rings. The experiment showed that light does not travel in straight lines but rather in wavelike undulations. The corpuscular theory came to be replaced with the wave theory of light. Knowing, therefore, that something can follow from something else even though what it follows from is false can be enormously useful. For this means that if you are uncomfortable with a conclusion seemingly validly derived from a premise, it is possible you are not in full agreement with the premise from which it is, apparently, correctly deduced. The trouble may therefore lie in the premise. Consider, for example, the following argument: f) Abortion is the destruction of a human fetus, and the destruc tion of a human fetus is the taking of a human life. If, therefore, the taking of a human life is murder, then so is abortion. What are the premises of this argument? What is the conclusion? Does the conclusion follow validly from the premises? How would you challenge this argument? The form of sound deductive arguments is equally useful. For if we reason validly from'true premises, we must necessarily arrive at a conclusion that is true whether or not we can test its truth directly.