Philosophical Adventures

Steven M. Cahn

• Publisher: Broadview Press
• Year: 2019
• ISBN:
  9781460406717
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

Philosophical Adventures is a clear, concise introduction to philosophy, covering an engaging set of topics: reasoning, free will, religious belief, ethics, well-being, politics, and education. Stylishly written and cogently argued, the book engages readers by using compelling examples to make complex ideas accessible. The book's distinctive and engaging content provides a welcoming path to understanding the appeal of philosophical inquiry.

PART I: REASONING

1

The Elements of Argument

Because philosophy calls for us to be reasonable, the question immediately arises: What is reason? The answer is found in this opening chapter, an earlier version of which I co-authored with Patricia Kitcher, now Professor of Philosophy at Columbia University, and George Sher, now Professor of Philosophy at Rice University. At one time we were colleagues in the Department of Philosophy at the University of Vermont, and I am grateful for their original collaboration.

We reason every day of our lives. Whether the topic is politics, morality, movies, or sports, we offer arguments to convince others that our views are reasonable. But what is an argument, and which arguments should be accepted?

Arguments

In ordinary parlance, an argument is simply a dispute. To philosophers, however, an argument is a collection of sentences consisting of one or more premises and a conclusion. The evidence you cite is your premise or premises; the statement you defend is your conclusion. Whenever you construct an argument, you need to take some claim as your premise. Of course, assuming the truth of a controversial claim in order to argue for what is obvious would be unconvincing. The direction of sensible argumentation is always from the more obvious to the less. Ideally, a reasoner will choose premises that are uncontroversial and argue that a more disputed, perhaps even surprising, conclusion follows from those unproblematic assumptions.

Logic is the branch of philosophy that studies the relations between premises and conclusion, establishing guidelines about which claims can be inferred from others. This task has been carried out with great success for deductive inference.

Deductive Arguments

The central concept of deductive logic is validity. An argument is valid whenever the truth of the premises guarantees the truth of the conclusion. In other words, in a valid argument the conclusion follows from the premises; that is, the conclusion cannot be false if the premises are true. Logic is not concerned with the truth of the premises or the truth of the conclusion but only with the relation between the premises and the conclusion.

In ordinary English “valid” and “true” are often used synonymously, yet their technical meanings are different. In philosophical terminology, statements are true or false, not valid or invalid. Arguments, however, are valid or invalid, not true or false. Thus you can make a true statement or present a valid argument, but you can’t speak validly or argue truthfully.

Note that a valid argument can have true or false premises, and they may be as numerous as wished. Here, for example, is a valid argument with true premises (such an argument is referred to as a sound argument):

PREMISE 1 The capital of Massachusetts is Boston.

PREMISE 2 Boston is the home of the Boston Red Sox.

CONCLUSION The capital of Massachusetts is the home of the Boston Red Sox.

In this example the two premises are true, and the conclusion follows from the premises.

Here is another valid argument, but in this case the first premise is false and the second is true.

PREMISE 1 All playwrights lived in Greece.

PREMISE 2 Shakespeare was a playwright.

CONCLUSION Shakespeare lived in Greece.

Although the first premise is false, the argument is nevertheless valid, because the conclusion follows from the premises. In other words, whether the premises are true, they imply the conclusion.

Now here is another valid argument, but this time both premises are false, yet they imply a true conclusion:

PREMISE 1 All canaries are polar bears.

PREMISE 2 All polar bears have feathers.

CONCLUSION All canaries have feathers.

Note also that even if the premises of an argument are all true and the conclusion is true, the argument may not be valid, as in this case:

PREMISE 1 Some roses are red.

PREMISE 2 Some violets are blue.

CONCLUSION Flowers give some people hay fever.

The problem is that while all the statements are true, the truth of the premises does not guarantee the truth of the conclusion, and that relation is the hallmark of a valid argument.

Thus a compelling deductive argument should be valid. Otherwise the premises will not lead us to accept the conclusion.

Deductive arguments, however, are not the only form of effective reasoning. We turn next to non-deductive arguments.

Non-Deductive Arguments

We encounter many good but non-deductive inferences in everyday and scientific discussions. Suppose, for example, that a particular drug is given a hundred thousand trials across a wide variety of people, and it never produces serious side effects. Even the most scrupulous researcher would conclude that the drug is safe. Still, this conclusion cannot be deductively inferred from the data. Here is the argument:

PREMISE In 100,000 trials, drug X produced no serious side effects.

CONCLUSION Drug X does not have any serious side effects.

Because a serious side effect may appear on the 100,001st trial, the premise could be true even though the conclusion is false. Hence the argument is deductively invalid, yet it is strong and should be accepted.

We can present many more good but deductively invalid arguments. Here is another example.

PREMISE 1 The dining room window is shattered.

PREMISE 2 A baseball is lying in the middle of the glass on the dining room floor.

PREMISE 3 A baseball bat is found on the ground in the yard outside the dining room.

CONCLUSION The dining room window was shattered by being hit with a baseball.

If we recognize only the standard of deductive validity, then the previous arguments—and all other arguments like these—will have to be dismissed as bad reasoning. That constraint on argumentation, however, is unacceptable. Why should we demand that the truth of the premises guarantees the truth of the conclusion? After all, we often suppose that a claim is not certain but highly probable. For instance, we would be willing to place a sizable bet that a roulette ball will not land on number 7 twenty times in a row. Yet no true premises about how roulette is played render that result impossible. Logic, therefore, has a second task. It needs to provide criteria for evaluating good but non-deductive inferences.

Induction

We believe that if a dry piece of paper is placed into the flame of a candle, the paper will burn. Why do we hold this belief? We reason that in the past dry paper placed into the flame of a candle always burned, so we infer that it will burn in the present case. This common type of reasoning is called induction. In it, we rely on similar, observed cases to infer that the same event or property will recur in as yet unobserved cases.

Of course, in different instances we have different amounts of evidence on which to draw. If only ten cases of a disease have been observed, then we will have much less confidence in predicting the course of the disease than if we had observed ten thousand cases. Philosophers often refer to our confidence in a claim as our strength of belief. Surely it should increase with the number of positive instances of the claim. Hence, for example, if you arrive in a new town and notice that all the buses you see on your first day are green, then as the days pass and you continue to observe only green buses, the strength of your belief that all the buses in town are green will increase.

While positive instances gradually confirm an inductive generalization, rendering it more and more reasonable, a negative instance defeats the generalization. To take a dramatic twentieth-century example, with the splitting of the first atom, the long-standing claim that atoms are indivisible particles of matter had to be relinquished.

Beside the sheer number of positive instances, another criterion for good inductive reasoning is that the evidence be varied. If you have observed buses in many different parts of town, then you are more justified in claiming that the town’s buses are all green than if you have only considered the buses on your own street.

Hypothesis Testing

All of us, especially scientists, test hypotheses as a form of non-deductive reasoning. For example, imagine that a problem has developed in a small rural town, where residents are falling sick at an alarming rate. The local doctor hypothesizes that the trouble has been caused by the opening of a new chemical plant that is emptying waste within a mile of one of the lakes that yields the town’s supply of drinking water. The hypothesis can be tested in a number of different ways. For instance, the residents might check the consequences of drinking water only from a lake not close to the chemical plant. Granted, the doctor’s hypothesis would fail such a test if, despite using water from a different lake, the sickness continued to spread. Yet the hypothesis might pass the test if drinking water from a different lake leads to the illness disappearing. This case indicates the way in which a hypothesis can be tested. Frequently we advance a claim whose truth or falsity we are unable to ascertain by direct observation. We cannot just look and see if the earth moves, or if the continents were once part of a single land mass, or if the butler committed the crime. In evaluating such hypotheses, we consider what things we would expect to observe if the hypothesis were true. Then we investigate to see if these expectations are confirmed. If so, then the hypothesis passes the test, and its success counts in its favor; if not, then the failure counts against the hypothesis.

Inference to the Best Explanation

Another common and indispensable type of non-deductible inference should be familiar to readers of detective stories. Sherlock Holmes, for instance, uses this type of reasoning in his first encounter with Dr. Watson in A Study in Scarlet.

I knew you came from Afghanistan. From long habit the train of thoughts ran so swiftly through my mind that I arrived at the conclusion without being conscious of intermediate steps. There were such steps, however. The train of reasoning ran, ‘Here is a gentleman of a medical type, but with the air of a military man. Clearly an army doctor, then. He has just come from the tropics, for his face is dark, and that is not the natural tint of his skin, for his wrists are fair. He has undergone hardship and sickness, as his haggard face says clearly. His left arm has been injured. He holds it in a stiff and unnatural manner. Where in the tropics could an English army doctor have seen much hardship and got his arm wounded? Clearly in Afghanistan.’ The whole train of thought did not occupy a second. I then remarked that you came from Afghanistan, and you were astonished.¹

Holmes’s argument is deductively invalid. Even though Watson has a deep tan and a wounded arm, perhaps he has never been in Afghanistan but obtained the tan in Argentina and the wound in a knife fight in Peru. Yet Holmes’s argument does provide considerable support for his claim that Watson had been in Afghanistan. Here is how Holmes’s reasoning works. He lists various facts, such as the military bearing, the tan, and the wounded arm. Then he uses them to infer a conclusion that would explain all of them. In this case, if Watson is a military doctor who just returned from active service in Afghanistan, that conclusion would explain why he has a tan, an injured arm, and so forth. The name for this type of reasoning is argument by inference to the best explanation, and it is closely related to hypothesis testing. There a hypothesis is supported when observations that can be deduced from the hypothesis are borne out. In argument by inference to the best explanation, the hypothesis is supported when it explains given facts. In either case the results can yield high probabilities, although not certainties.

Argument Analysis

Having examined various types of inference, let us now consider how this information may be used in analyzing reasoning. The basic task of argument analysis is to provide a clear formulation of the chain of argumentation presented in ...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Contents
• Preface
• Part I: Reasoning
• Part II: Free Will
• Part III: Religious Belief
• Part IV: Ethics
• Part V: Well-Being
• Part VI: Society
• About the Author
• Permissions Acknowledgments