An Introduction to Philosophy, Second Edition

Created Nov. 6, 2024 by Marc Skuster

Learning Objectives - On completing this chapter, you will be able to:

  • Discuss the role of argument and dialectic in Philosophy.
  • Explain the concept of truth as “correspondence.”
  • Distinguish between deductive and inductive reasoning.
  • Explain the two steps of argument evaluation.
  • Evaluate deductive arguments for soundness and inductive arguments for cogency.
  • Define the concept of “fallacy” and illustrate this concept with examples of informal fallacies.

Introduction

Arguments

As a kind of inquiry, philosophy is aimed at establishing knowledge and understanding. Even where certain knowledge about a particular issue can’t be had, there are often interesting things to learn about why we can’t have certainty and what sorts of less-than-certain reasons there are for or against holding a position on that issue. So, rational inquiry may be interesting and fruitful even when we are denied straight-forward answers to our initial questions. Once we raise a philosophical issue, whether about the nature of justice or about the nature of reality, we want to ask what can be said for or against the various possible answers to our question. Here we are engaged in formulating arguments. Some arguments give us better reasons or accepting their conclusions than others. Once we have formulated an argument, we want to evaluate the reasoning it offers. If you want to know what philosophers do, this is a pretty good answer: philosophers formulate and evaluate arguments.

Your introduction to philosophy should be as much a training in how to do philosophy as it is a chance to get to acquainted with the views of various philosophers. To that end, you should carefully study the sections below on arguments.


Dialectic

Once a philosophical position is considered, we want to ask what arguments can be advanced in support of or against that issue. We then want to examine the quality of the arguments.

Evaluating flawed arguments often points the way towards other arguments and the process of formulating, clarifying, and evaluating arguments continues. This method of question and answer in which we recursively formulate, clarify, and evaluate arguments is known as dialectic.

Dialectic looks a lot like debate, but a big difference lies in the respective goals of the two activities. The goal of a debate is to win by persuading an audience that your position is right and your opponent’s is wrong. Dialectic, on the other hand, is aimed at inquiry. The goal is to learn something new about the issue under discussion. Unlike debate, in dialectic your sharpest critic is your best friend. Critical evaluation of your argument brings new evidence and reasoning to light. The person you disagree with on a philosophical issue is often the person you stand to learn the most from (and this doesn’t necessarily depend on which of you is closer to the truth of the matter).

Dialectic is sometimes referred to as the Socratic Method after the famous originator of this systematic style of inquiry. We will get introduced to some of Plato’s dialogues chronicling the exploits of Socrates in the next chapter on Ancient Greek Philosophy. This will give you a good sense for how the Socratic Method works. Then watch for how the Socratic Method is deployed throughout the rest of the course.



Truth

As varieties of rational inquiry, it’s natural to think that science and philosophy are mainly concerned with getting at the truth about things. There are some interesting and some confused challenges to the idea that philosophy and science are truth oriented. But for now let’s assume that rational inquiry is truth oriented and address a couple of questions about truth. Let’s focus on just these two:

  • What is it for a claim to be true?
  • How do we determine that a claim is true?

It’s important to keep these two questions separate. Questions about how we know whether something is true are epistemic questions. But the question of what it is for something to be true is not an epistemic issue. The truth of a claim is quite independent of how or whether we know it to be true. If you are not sure about this, consider the claim that there is intelligent life on other planets and the claim that there is no intelligent life on other planets. I assume we don’t know which of these two claims is true, but surely one of them is. Whichever of these claims is true, its being true doesn’t depend in any way on whether or how we know it to be true. There are many truths that will never be known or believed by anyone, and appreciating this is enough to see that the truth of a claim is not relative to belief, knowledge, proof, or any other epistemic notion.


What Does It Mean for a Claim to be True?

But then what is it for a claim to be true? The ordinary everyday notion of truth would have it that a claim is true if the world is the way the claim says it is. And this is pretty much all we are after. When we make a claim, we represent some part of the world as being a certain way. If how my claim represents the world fits with the way the world is, then my claim is true. Truth, then, is correspondence, or good fit, between what we assert and the way things are.

Is Truth Relative to Meaning, Knowledge, Belief, or Opinion?

There is a further potential source of confusion about truth that might be worth addressing at this point. Words and sentences can be used in lots of different ways. Even if we are not being inventive with language, there is lots of vagueness and ambiguity built into natural language. A tempting pitfall in thinking about truth is to think that truth is somehow relative to meaning or open to interpretation.

We’d all agree that it’s true that dogs are canines. But suppose we used the word “dog” to refer to cats instead. A word is just a sound or a string of letters. We can, in principle, attach any meaning we like to the word “dog.” If we used the word “dog” to refer to cats, then the sentence “Dogs are canines” would be false. Doesn’t this make truth relative to meaning or interpretation? Well, in a way yes, but not really.

The truth of sentences, bits of language, is relative to meaning. But the relativity at issue here is entirely linguistic. It’s simply the result of the meaning of words and sentences being relative to linguistic convention. But our everyday notion of truth is not about linguistic convention any more than it is about knowledge or belief. Our notion of truth is fundamentally about the correspondence between what is meant by a sentence and the way the world is. Philosophers often refer to what is meant or expressed by a sentence as a proposition. While a sentence is a piece of language that has a meaning, the proposition it expresses is not itself a piece of language.

Consider “Schnee ist weiss” and “Snow is white.” The first sentence is German for "Snow is white." These are distinct sentences, and this is clear because they belong to different languages. But they say the same thing. They both express the proposition that snow is white.  Although we are stuck with using English to refer to the proposition, that doesn’t mean the proposition is linguistic. We use English to refer to lots of things that aren’t themselves part of language--for instance, dogs and cats.

So the proposition expressed by a sentence is not itself a linguistic thing. Being a non-linguistic thing, the proposition does not have a meaning. Rather the proposition is what is meant. For a bit of language to be open to interpretation is for us to be able to attach different meanings to it. But the meanings themselves are not open to further interpretation. And it is the proposition, what is meant by the sentence, that is the fundamental bearer of truth or falsity. A proposition is true when it represents things the way they are. So when I speak of arguments consisting of claims you might bear in mind that its propositions, not sentences I’m talking about. If we misinterpret the sentence, then we are not dealing with the claim being made, and hence we probably don’t fully understand the argument. Getting clear on just what an argument says is critical to the dialectical process.

Even if you are exceptionally bright, you probably found the last couple paragraphs rather challenging. That’s OK. You might work through them again more carefully and come back to it in a day or two if it’s still a struggle. The path to becoming a better critical thinker is more like mountain climbing than a walk in the park, but with this crucial difference: no bones get broken when you fall off an intellectual cliff. So you are always free to try to scale it again. We can sum up the key points of the last few paragraphs as follows:

  • We use sentences, bits of language, to express propositions.
  • The proposition, what is meant by the sentence, represents the world as being some way.
  • The proposition is true when it represents the world in a way that corresponds to how the world is.
  • Truth, understood as correspondence between a claim (a proposition) and the way the world is, is not relative to meaning, knowledge, belief, or opinion.

Hopefully we now have a better grip on what it is for a claim to be true. A claim is true just when it represents things as they are. As is frequently the case in philosophy, the real work here was just getting clear on the issue. Once we clearly appreciate the question at hand, the answer seems pretty obvious. So now we can set aside the issue of what truth is and turn to the rather different issue of how to determine what’s true.

How Do We Determine That A Claim Is True?

The common sense, everyday way to assess a claim for truth or falsity is to consider the reasons for holding it or rejecting it. Sometimes good reasons take the form of simple observations. I have a good reason for thinking my bicycle has a flat tire when I see the tire sagging on the rim or hear air hissing out of the tube. But often the business of identifying and evaluating reasons is a bit more involved. Since philosophy proceeds by formulating and evaluating the reasons for and against holding various positions, we will want to take a closer look at just how this goes.

We will do so in the remainder of this chapter with the informal introduction to logic and critical thinking.


Arguments

An argument is a reason for taking something to be true. Arguments consist of two or more claims, one of which is a conclusion. The conclusion is the claim the argument purports to give a reason for believing. The other claims are the premises. The premises of an argument taken together are offered as a reason for believing its conclusion.


Evaluating Arguments

Some arguments provide better reasons for believing their conclusions than others. In case you have any doubt about that, consider the following examples:

Sam is a line cook.
Line cooks generally have good of kitchen skills.
So, Sam can probably cook well.

Sam is a line cook.
Line cooks generally aren’t paid very well.
So, Sam is probably a millionaire.

The premises in the first argument provide pretty good support for thinking Sam can cook well. That is, assuming the premises in the first argument are true, we have a good reason to think that its conclusion is true. The premises in the second argument give us no reason to think Sam is a millionaire. So whether or not the premises of an argument support its conclusion is a key issue. Now consider these examples:

Boston is in Massachusetts.
Massachusetts is east of the Rockies.
So Boston is east of the Rockies.

Boston is in California.
California is west of the Rockies.
So Boston is west of the Rockies.

Again, the first of these two arguments looks pretty good, the second not so much. But the problem with the second argument here is different. If its premises were true, then we would have a good reason to think the conclusion is true. That is, the premises do support the conclusion. But the first premise of the second argument just isn’t true. Boston is not in California. So the latter pair of arguments suggests another key issue for evaluating arguments. Good arguments have true premises.

That is pretty much it. A good argument is an argument that has true premises that, when taken together, support its conclusion. So, evaluating an argument involves just these two essential steps:

  • Determine whether or not the premises are true.
  • Determine whether or not the premises support the conclusion (that is, whether we have grounds to think the conclusion is true if all of the premises are true).

Determining the Truth of Premises

Determining whether an argument’s premises are true often involves evaluating further arguments in support of those premises. An argument might be the last link in a long chain of reasoning. In this case, the quality of the argument depends on the whole chain. And since arguments can have multiple premises, each of which might be supported by further arguments, evaluating one argument might be more involved yet, since its conclusion is really supported by a rich network of reasoning, not just one link and then another. While the potential for complication should be clear, the basic idea should be pretty familiar. Think of the regress of “why” questions with which many of us tormented our parents as children. Even at a young age we understood that the reasons for believing one thing can depend on the reasons for believing a great many other things.

However involved the network of reasons supporting a given conclusion might be, it seems that there must be some starting points. That is, it seems there must be some reasons for believing things that don’t themselves need to be justified in terms of further reasons. Otherwise the network of supporting reasons would go on without end. The issue we are facing here is one of identifying the ultimate foundations of knowledge and justified belief. This is a big epistemological issue and we will return to it later in the course. For now, let’s consider one potential answer we are already familiar with. In the sciences our complex chains of reasoning seem to proceed from the evidence of the senses. We think that evidence provides the foundation for our edifice of scientific knowledge. Sounds great for science, but where does this leave philosophy? Does philosophy entirely lack evidence on which its reasoning can be based?

Philosophy does have a kind of evidence to work from and that evidence is provided by philosophical problems. When we encounter a problem in philosophy this often tells us that the principles and assumptions that generate that problem can’t all be correct. This might seem like just a subtle clue that leaves us far from solving the big mysteries. But clues are evidence just the same. As we will discuss in our chapter on the philosophy of science, science doesn’t really have it much easier. Sensory evidence by itself doesn’t tell us as much about the nature of the world as we’d like to suppose. Scientific evidence provides clues, but there remains a good deal of problem solving to do in science as well as in philosophy.

So we can assess the truth or falsity of the premises of an argument by examining evidence or by evaluating further argument in support of the premises.

Determining Whether or Not the Premises Support the Conclusion

Now we will turn to the other step in evaluating arguments and consider the ways in which premises can support or fail to support their conclusions. The question of support is distinct from the question of whether the premises are true. When we ask whether the premises support the conclusions we are asking whether we’d have grounds for accepting the conclusion assuming the premises are true. In answering this question we will want to apply one of two standards of support: deductive validity or inductive strength.

Deductive Validity

The deductive standard of support is validity. An argument counts as deductive whenever it is aiming at this standard of support. Deductive validity is the strictest standard of support we can uphold. In a deductively valid argument, the truth of the premises guarantees the truth of the conclusion. Here are two equivalent definitions of deductive validity:

(D)A valid argument is an argument where if its premises are true, then its conclusion must be true.

(D’)A valid argument is an argument where it is not possible for all of its premises to be true and its conclusion false.

Here are a two examples of deductively valid arguments

If Socrates is human, then Socrates is mortal.
Socrates is a human.
Therefore, Socrates is mortal.

All monkeys are primates.
All primates are mammals.
So, all monkeys are mammals.

If you think about these two examples for a moment, it should be clear that there is no possible way for the premises to all be true and the conclusion false. The truth of the conclusion is guaranteed by the truth of the premises. In contrast, the following argument is not valid:

If Sue misses her plane, she will be late for the conference.
Sue is late for the conference.
Therefore, she missed her plane.

Again, to say that an argument is deductively valid is to say that it is impossible for all of its premises to be true and its conclusion to be false. To see why the last argument is not valid, try to think of a possible scenario that makes both of the premises true and the conclusion false. One scenario is where Sue catches her plane, but her cab from the airport gets stuck in traffic. If we can think of any possible way for the premises of an argument to be true and its conclusion false, then we have shown that the conclusion does not deductively follow from the premises. That is, we’ve shown that the argument is not valid.

Our intuitive test for validity is to think about whether it is possible for the argument’s premises to be true and its conclusion to be false. A key point to notice here is that validity is not directly about the truth or falsity of the premises or the conclusion. The concept of validity is really a concept about what is and isn’t logically possible. A deductively valid argument may or may not have true premises. Consider this argument:

All stars are bodies that shine steadily.
All planets are stars.
All planets are bodies that shine steadily.

Both of the premises in this argument are false, but the argument is still valid. Suppose, contrary to fact, that the premises were true. It should be easy to see that the conclusion would have to be true if this were the case. Validity isn’t about whether the premises or the conclusion are in fact true. It is only about whether the conclusion logically follows from the premises.

A deductively valid argument only provides one with a good reason for believing its conclusion if its premises are true. If a deductively valid argument has all true premises, we say that it is deductively sound. For an argument to be deductively sound is one way for it to pass both steps (1) and (2) above for evaluating arguments.

The deductive arguments we’ve looked at here are pretty intuitive. We only need to think about whether the conclusion could be false even if the premises were true. But most deductive arguments are not so obvious. Logic is the science of deductive validity. Philosophy has made some historic advances in logic over the past century. Bertrand Russell, who we got acquainted with in the last chapter, was among the key contributors to early developments in logic over the 20th century. In the next chapter we will get acquainted with the first logician, Aristotle.

Inductive Strength

Consider the following:


Sam is a line cook.
Line cooks generally have good of kitchen skills.
So, Sam can probably cook well.

This is a decent argument. The premises do support the conclusion. And yet it might be that both premises are true and the conclusion is false. Sam could be a brand new cook hired because he’s the manager’s son who has never cooked in his life. Many arguments give us good reasons for accepting their conclusions even if their premises being true fails to completely guarantee the truth of the conclusion. This suggests that we need another standard of support for arguments that aim at giving us pretty good but not absolutely compelling grounds for accepting their conclusions. And this standard of support is called inductive strength. Here are two equivalent ways of defining inductive strength:

(I)An inductively strong argument is an argument in which if its premises are true, its conclusion is probably to be true.

(I’)An inductively strong argument is an argument in which it is improbable that its conclusion is false given that its premises are true.

If you look again at the earlier definitions for deductive validity you will find a good deal of similarity. The only difference is in the use of the words "probably" rather than “must be” in the first definition, and “improbable” rather than "impossible" in the second. This is a big difference. As in the case of validity, when we say that an argument is strong, we are not assuming that its premises are true. We are only claiming that if the premises are true then the conclusion is likely to be true. Corresponding to the notion of deductive soundness, an inductive argument that is both strong and has true premises is called a cogent inductive argument. Unlike the case if deductively sound arguments, it is possible for an inductively cogent argument to have true premises and a false conclusion.

Lots of good reasons for holding a belief fall short of the standard of deductive validity. The sort of reasoning you were taught as “the scientific method” in secondary school is inductive reasoning. As it is taught in high school, the scientific method consists of formulating a general hypothesis and testing it against a large sampling of data. If the data is consistent with the hypothesis, then the hypothesis is considered confirmed by the data. Here a limited amount of evidence is taken to support a broader, more general hypothesis. In the simplest case, inductive reasoning involves inferring that something is generally the case from a pattern observed in a limited number of cases. For instance, if we were to conduct a poll of 1000 voters in the same city and 600 of them claimed to be Democrats, then we could inductively infer that 60% of the voters in this city are Democrats. This is a form of reasoning that we call inductive generalization.  The results of the poll give a pretty good reason to think that around 60% of the voters in the city involved are Democrats. But the results of the poll don’t guarantee this conclusion. It is possible that only 50% of the voters in Surf City are Democrats and Democrats were, just by luck, over represented in the 1000 cases we considered.

When evaluating deductive arguments for validity we ask if it is possible for the premises to be true and the conclusion to be false. This is either possible or it isn’t. Possibility does not admit of degrees. But probability does. The truth of the conclusion of an inductive argument can be probable to a greater or lesser degree. An argument either is or isn’t valid. But inductive arguments can be more or less strong. We can identify a few factors that bear on the degree of strength an inductive argument has. One is how much evidence we have looked at before inductively generalizing. Our inductive argument above would be stronger if we drew our conclusion from a poll of 100,000 voters, for instance. And it would be much weaker if we had only polled 100. Also, the strength of an inductive argument depends on the degree to which the observed cases represent the makeup of the broader class of cases. So our inductive argument will be stronger if we randomly select our 1000 voters from all neighborhoods rather than selecting them only from an affluent suburb.

So far, we’ve only discussed inductive generalization, where we identify a pattern in a limited number of cases and draw a more general conclusion about a broader class of cases. Inductive argument comes in other varieties as well. In the example we started with about Sam the line cook, we inductively inferred a prediction about Sam based on a known pattern in a broader class of cases. Argument from analogy is another variety of inductive reasoning that can be quite strong. For instance, I know that my house cat is very similar to cougars in the wild. Knowing that my cat can jump great heights, it would be reasonable to expect that by analogy, or based on this similarity, cougars can jump well too.

There are further varieties of argument that aim at the standard of inductive strength, but we will discuss just one more in detail now. Abduction is inference to the best explanation. Detective work provides a good example of abductive argument. When Holmes discovers Moriarty’s favorite brand of cigar and a bullet of the sort fired by Moriarty’s gun at a murder scene, inference to the best explanation suggests that Moriarty was the killer. That Moriarty committed the murder provides the overall best explanation of the various facts of the case.

The 19th century American pragmatist and logician, Charles Sanders Peirce offers the Surprise Principle as a method for evaluating abductive arguments. According to the surprise principle, we should count one explanation as better than competing explanations if it would render the facts we are trying to explain less surprising than competing explanations. The various clues in the murder case are among the facts we want explained. The presence of the cigar and the bullet casing at the murder scene is much less surprising if Moriarty committed the murder than if the maid did it. Inference to the best explanation aims at strength. So a strong abductive argument in this case needn’t rule out the possibility that the murder was committed by Moriarty’s evil twin who convincingly frames his brother. There might an argument against the death penalty lurking nearby. Inference to the best explanation is worth more attention than if often receives. This kind of reasoning is pervasive in philosophy and science, but seldom gets much notice as an integral part of the methods of rational inquiry.

Fallacies

A fallacy is just a mistake in reasoning. Humans are not nearly as rational as we’d like to suppose. In fact we are so prone to certain sorts of mistakes in reasoning that philosophers and logicians refer those mistakes by name. For now I will discuss just one by name but in a little detail. Watch for explanations of other fallacies over the course of the class. For pretty thorough catalog of logical fallacies, I’ll refer to you The Fallacy Files.

“Ad hominem” is Latin for “against the man.” It is the name for the fallacy of attacking the proponent of a position rather than critically evaluating the reasons offered for the proponent’s position. The reason ad hominem is a fallacy is just that the attack on an individual is simply not relevant to the quality of the reasoning offered by that person. Attacking the person who offers an argument is unrelated to determining whether or not the premises of the argument are true or support the conclusion. Ad hominem is a particularly rampant and destructive fallacy in our society. What makes it so destructive is that it turns the cooperative social project of inquiry through conversation into polarized verbal combat. This fallacy makes rational communication impossible while it diverts attention from interesting issues that often could be fruitfully investigated.

Here is a classic example of ad hominem: A car salesman argues for the quality of an automobile and the potential buyer discounts the argument with the thought that the person is just trying to earn a commission. There may be good reason to think the salesman is just trying to earn a commission. But even if there is, this is irrelevant to the evaluation of the reasons the salesman is offering. The reasons should be evaluated on their own merits. Notice, it is easy to describe a situation where it is both true that the salesman is just trying to earn a commission and true that he is making good arguments. Consider a salesman who is not too fond of people and cares little for them except that they earn a commission for him. Otherwise he is scrupulously honest and a person of moral integrity. In order to reconcile himself with the duties of a sales job, he carefully researches his product and only accepts a sales position with the business that sells the very best. He then sincerely delivers good arguments for the quality of his product, makes lots of money, and dresses well. This salesman must have been a philosophy major. The customer who rejects his argument on the ad hominim grounds that he is just trying to earn a commission misses an opportunity to buy the best. The moral of the story is just that the salesperson’s motive is logically independent of the quality of his argument.

Review and Study

Review Questions:

  • How does dialectic differ from debate?
  • What is it for a claim to be true? How does this issue differ from that of determining whether a claim is true?
  • Explain our everyday concept of truth in terms of correspondence.
  • What is an argument? How do we evaluate arguments?
  • What does it mean for the premises of an argument to support its conclusion, and what are the two standards of support?
  • Explain the surprise principle and illustrate its use in evaluating an inference to the best explanation.
  • What is a fallacy? Learn about a fallacy or two on The Fallacy Files and report back.

Further Reading;

Names, Terms, and Concepts:

  • Argument
  • Dialectic
  • Socratic Method
  • Proposition
  • Correspondence
  • Premise
  • Conclusion
  • Deductive Validity
  • Inductive Strength
  • Deductive Soundness
  • Inductive Cogency
  • Inductive Generalization
  • Argument from Analogy
  • Abduction
  • Surprise Principle
  • Fallacy
  • Ad Hominem



Return to top