Argument and Evidence: How Do I Decide What to Believe? 37

1.3 ARGUMENT AND EVIDENCE: HOW DO I DECIDE WHAT TO BELIEVE?

In section 1.0 I said that philosophy is the search for fundamental beliefs that are justifi ed. When you read what a philosopher has written, avoid the bottom-line syndrome. This prob-lem involves simply agreeing or disagreeing with the author’s conclusion without paying attention to whether the philosopher has provided good reasons for believing the conclu-sion. Responding in this way defeats a major goal of philosophy—the goal of seeing whether our beliefs or those of others are justifi ed. For example, someone who believes in God (a theist) would agree with the conclusion of Thomas Aquinas’s arguments (i.e., “There is a God”). But some theists do not think that Aquinas’s arguments are strong. It is important to realize that in demonstrating that an argument is weak, we have not shown that its conclusion is false. We have merely shown that the reasons the author has given for the conclusion do not guarantee its truth. Nevertheless, if the only arguments that can be found to support a conclusion are weak, we really have no reason to suppose that the conclu-sion is true. Remember, evaluating philosophies is not like tasting foods. (“I like this. I don’t like that.”) Instead, it is an attempt to fi nd objective reasons why we should or should not believe that a claim is true. In this section, I briefl y cover some techniques for evaluating philosophical claims and arguments.

EVALUATING PHILOSOPHICAL CLAIMS AND THEORIES

In order to evaluate and choose between competing philosophical claims and theories, philosophers have agreed on a number of criteria, or tests. We will consider the six most common ones. I have formulated each criterion so that it contains a keyword that begins with the letter c in order to make the points easy to remember. The criteria are

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(1) conceptual clarity, (2) consistency, (3) rational coherence, (4) comprehensiveness, (5) com-patibility with well-established facts and theories, and (6) having the support of compelling arguments. We will briefl y look at each one in turn.

Clarity

Conceptual clarity is the fi rst test that a philosophy must pass. If the terms or concepts in which the philosophy is expressed are not clear, then we don’t know precisely what claim is being put forth. Suppose someone says, “The only thing in life that has value is pleasure.” We need to ask, What does the author mean by “pleasure”? Is the term referring only to physical sensations, or do intellectual pleasures count? If it makes me feel good to sacrifi ce my own needs for those of others, am I really pursuing pleasure?

Consistency

Consistency is the second test that a philosophy must pass. A philosophy cannot contain any contradictions. One way a philosophy fl unks this test is through logical inconsistency, which consists in making two assertions that could not both be true under any possible circumstances. The most obvious case of this inconsistency would be any claim of the form, “A is true and not-A is true.” For example, if I claim that God determines everything that happens in the world at the same time that I claim that humans have free will, I appear to have an inconsistency. The fi rst claim implies that God determines what choices we make, but this claim seems to confl ict with the claim that we freely make our own choices. The terms determines and free will would have to be defi ned differently than they normally are to avoid the inconsistency. A second kind of inconsistency is more subtle. It is called self-referential inconsistency, and it occurs if an assertion implies that it itself cannot be true, or cannot be known to be true, or should not be believed. My statement that “All opinions are false” implies that the opinion I just expressed is false. Similarly, my claim that “Only statements that can be scientifi cally proven should be believed” is a statement that cannot be scientifi cally proven.

Coherence

Rational coherence is a criterion that considers how well the various parts of a philosophy “hang together.” The elements of a philosophy may not be explicitly contradictory, but they can still fail to fi t together very well. A philosopher who believes that God acts in the world but who fails to explain how that belief fi ts together with the belief that nature runs according to universal physical laws has articulated a philosophy that lacks coherence. Similarly, philosopher René Descartes argued that humans are made up of a physical body and a nonextended, nonphysical mind. Although he believed that the two interacted, he failed to make clear how such different types of substances could causally infl uence one another. This gap in his theory earned him low points on the coherence criterion in the minds of many critics.

Comprehensiveness

We evaluate a philosophy positively if it makes sense out of a wide range of phenomena; we evaluate it negatively if it ignores signifi cant areas of human experience or raises more questions than it answers. A philosophy that illuminates humanity’s scientifi c, moral,

38 CHAPTER 1 INTRODUCTION TO THE PHILOSOPHICAL JOURNEY

logical inconsis-tency two assertions that could not both be true under any possible circumstances

self-referential inconsistency an assertion that implies that it itself cannot be true, cannot be known to be true, or should not be believed

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aesthetic, and religious experience is better than one that explains only science but ignores the rest of human experience. To take a more specifi c example, a philosopher who claims that all knowledge is based on sensory data but who fails to explain how we can have mathematical knowledge or moral knowledge falls short on this criterion. Similarly, a phi-losopher who claims that all morality is derived from the Ten Commandments but who fails to explain how some cultures have developed similar moral principles even if they never heard of these commandments fails in terms of comprehensiveness.

Compatibility

Compatibility with well-established facts and theories is important because a good theory (in philosophy or science) is one that increases our understanding by unifying our knowl-edge. Hence, a theory that fl ies in the face of the rest of our understanding of the world may require us to lose more than we gain. For example, a philosophical theory about the mind should fi t with the well-established fi ndings of biology and psychology. There are,

Argument and Evidence: How Do I Decide What to Believe? 39

Relativity (1953) by M. C. Escher. In this “impossible” picture, the artist presents a scene composed of many incompatible planes. This could be viewed as a visual analogy of a philosophy which violates the criteria of consistency and rational coherence. This violation occurs when the elements of a philosopher’s theory either contradict each other or do not fi t together in a coherent way.

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however, exceptions to this rule. Throughout history, well-argued theories in philosophy and science have sometimes required us to violate common sense and abandon centuries-old beliefs, resulting in new knowledge. Nevertheless, we should do so only when the new theory is better than its competitors and promises to replace our current beliefs with an increase in understanding.

Compelling Arguments

The fi nal criterion for evaluating philosophical claims and positions is that they must have the support of compelling arguments. Philosophy is more than an intellectual cafeteria where we pick and choose what we like. Philosophers are making claims about what is true, what is real, and what is morally good. The claims that different philosophers make often confl ict with each other. Hence, they cannot all be true. As you read through the chapters of this book, you will have to decide which of the many confl icting claims are worthy of your belief. Even if a philosophy can pass on the fi rst fi ve criteria, you do not have suffi cient grounds for accepting it. You must look at what reasons the philosopher has provided or what further reasons you yourself can fi nd for being convinced of the truth of the position you are considering. An argument attempts to show that from certain true (or plausible) statements, the claim under consideration either necessarily follows or is highly probable. The next section covers the basics of the nature of arguments to get you thinking about this issue. I cover this topic in more detail in the appendix in the back of the book, where I survey various argument forms and discuss which ones are logically compelling and which ones are not.

THE NATURE OF ARGUMENTS

Philosophers attempt to establish the truth of their claims by means of arguments. But the word argument has two different meanings in everyday discourse. Suppose that two students were discussing whether there is a God, and they began shouting at each other, saying, “Yes there is,” “No there isn’t,” “Yes there is,” “No there isn’t.” If the exchange began to be quite heated, we might say that they were having an argument. In this context, argument would mean “a contentious dispute.” However, this defi nition is not what philosophers mean by argument. In philosophy, an argument is a set of statements in which one or more of the statements attempt to provide reasons or evidence for the truth of another statement. A premise is a statement in an argument that serves to provide evidence for the truth of a claim. A conclusion is the statement in an argument that the premises are claimed to support or imply.

An important step in analyzing an argument is deciding which statements are the prem-ises and which is the conclusion. Often the conclusion is the last statement in a passage. However, an author may place the conclusion fi rst or even in the middle. Using common sense and grasping the author’s intentions are the best ways to fi gure out the elements of a particular argument. Key terms are often used to indicate which statements are premises and which are conclusions. Premise indicators are terms that usually indicate that a premise will follow. Typical examples of premise indicators are since, because, for, given that. Conclusion indicators are terms that usually indicate that a conclusion will follow. Typical examples of conclusion indicators are therefore, so, hence, thus, consequently.

1 INTRODUCTION TO THE PHILOSOPHICAL JOURNEY

argument a set of statements in which one or more of the statements attempt to provide reasons or evidence for the truth of another statement

premise a statement in an argument that serves to provide evidence for the truth of a claim

conclusion the statement in an argument that the premises are claimed to support or imply

premise indicators terms that usually indicate that a premise will follow

conclusion indicators terms that usually indicate that a conclusion will follow

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