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- Herausgeber: John Wiley & Sons
- Kategorie: Geisteswissenschaft
- Serie: Key Concepts in Philosophy
- Sprache: Englisch
What is truth? Is there anything that all truths have in common that makes them true rather than false? Is truth independent of human thought, or does it depend in some way on what we believe or what we would be justified in believing? In what sense, if any, is it better for beliefs or statements to be true than to be false?
In this engaging and accessible new introduction Chase Wrenn surveys a variety of theories of the nature of truth and evaluates their philosophical costs and benefits. Paying particular attention to how the theories accommodate realist intuitions and make sense of truth’s value, he discusses a full range of theories from classical correspondence to relatively new deflationary and pluralist accounts. The book provides a clear, non-technical entry point to contemporary debates about truth for non-specialists. Specialists will also find new contributions to those debates, including a new argument for the superiority of deflationism to causal correspondence and pluralist theories.
Drawing on a range of traditional and contemporary debates, this book will be of interest to students and scholars alike and anyone interested in the nature and value of truth.
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Seitenzahl: 340
Veröffentlichungsjahr: 2014
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Table of Contents
Key Concepts in Philosophy Series
Title page
Copyright page
Dedication
Preface and Acknowledgments
1: What is Truth?
1.1 Truth and the Truth
1.2 Truth Bearers
1.3 Being True and Being Taken to be True
1.4 What Lies Ahead
Further Reading
2: Objectivity
2.1 Three Pictures of Reality
2.2 Realism
2.3 Relativism
2.4 Anti-Realism
2.5 Objectivity and the Equivalence Principle
Further Reading
3: Truth and Value
3.1 Is Truth Essentially a Kind of Goodness?
3.2 What Makes Truth Valuable?
3.3 Conclusion
Further Reading
4: Epistemic Theories of Truth
4.1 Skepticism and What Our Tests Test
4.2 The Coherence Theory of Truth
4.3 Problems for Coherentism
4.4 Pragmatic Theories of Truth
4.5 Epistemic Theories and the Equivalence Principle
4.6 Epistemic Theories, Realism, and Anti-Realism
4.7 Epistemic Theories and the Value of Truth
4.8 Final Assessment of Epistemic Theories
Further Reading
5: Correspondence Theories of Truth
5.1 The Idea that Truth Depends on the World
5.2 Classical Correspondence Theories
5.3 From Classical to Causal Correspondence
5.4 Problems for Causal Correspondence
5.5 Truthmakers
5.6 The Scope Problem
5.7 The Equivalence Principle, Realism, and the Value of Truth
Further Reading
6: Deflationary Theories of Truth
6.1 A New Way to Think About Truth
6.2 The Redundancy Theory
6.3 Disquotationalism
6.4 Minimalism
6.5 Resolving the Explanatory and Evidentiary Problems
6.6 Deflationism, the Equivalence Principle, and Realism
6.7 Deflationism and the Value of Truth
Further Reading
7: Pluralist Theories of Truth
7.1 Truth Monism and Truth Pluralism
7.2 The Scope Problem Again
7.3 Two Problems for Deflationism
7.4 Simple Pluralism and Wright's View
7.5 Simple Pluralism, Mixed Compounds, and Mixed Inferences
7.6 Alethic Functionalism
7.7 Objections to Pluralist Theories of Truth
7.8 Pluralism's Scorecard
Further Reading
8: Deflationism Revisited
8.1 Advancing the Debates
8.2 Common Ground and Methodological Deflationism
8.3 Deflationism vs. the Causal Correspondence Theory
8.4 Deflationism vs. Pluralism
8.5 Conclusion
References
Index
Key Concepts in Philosophy Series
Copyright © Chase Wrenn 2015
The right of Chase Wrenn to be identified as Author of this Work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.
First published in 2015 by Polity Press
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Preface and Acknowledgments
This book aims to provide an accessible overview of the philosophical debates concerning the metaphysics of truth. It focuses on three sets of issues. First, and most centrally, is the question of the nature of truth. What does it mean for a claim to be true, and is there anything true claims have in common that makes them true? Second is the question of objectivity. Are there claims whose truth is mind-independent, or does truth always depend on what people believe or what could be known? Third is the question of truth's value. How, if at all, is it better for beliefs to be true than false?
I have tried throughout this book to presuppose only as much background knowledge of logic and philosophy as a third- or fourth-year undergraduate would have. Consequently, I have generally avoided technical issues arising in connection with the semantic paradoxes (such as that posed by ‘This sentence is false’) and the formal details of alternatives to classical logic. Where necessary, discussion of those issues proceeds informally and omits many technical details. Burgess & Burgess (2011) is an excellent resource for those who are interested in how the semantic paradoxes and other issues in philosophical logic bear on the metaphysical problems discussed in this book.
The heart of this book (Chapters 4–7) surveys correspondence, epistemic, deflationist, and pluralist accounts of truth. These chapters explain what motivates the theories, as well as some of their most important advantages and disadvantages. The final, eighth chapter sets aside the pros-and-cons approach and argues for the superiority of the deflationary approach to its main rivals, correspondence and pluralist theories. My hope is that that chapter will advance the debates discussed earlier in the book and thereby give students a glimpse of how they can be carried forward.
I owe thanks to Michael Lynch for encouraging me to write this book, and to my editor, Emma Hutchinson, for her help throughout the process. The book itself has been greatly improved by fruitful discussions with a number of people, especially Michael Horton and Jeremy Kelly, whose detailed comments and criticism were invaluable. Two anonymous readers for Polity Press also provided comments that helped to make this book much better than it would have been otherwise.
Feedback from the students in my 2013 seminar on truth at the University of Alabama played a crucial role in the final revisions of this book. I am very grateful to those students, including Marissa Abrams, Mitchell Dykstra, Trevor Gant, Madaline Hargrove, Trent Moore, Patrick Norton, Matthew O'Brien, Samuel Rankin, Michael Reagan, Hunter Rodriguez, and Tiffany Simms. Thanks are also due to my research assistants, Mitchell Dykstra and Matthew O'Brien, for their excellent help in preparing the manuscript.
1
What is Truth?
It is true that the earth is closer to the sun in the northern hemisphere's winter than in the northern hemisphere's summer. It is not true that the Himalayas are older than the Appalachians. What's the difference? What does it mean for something to be true, or for it not to be? What, to be succinct, is truth? This book is about some of the ways philosophers have tried to answer that question.
As is often the case, answering the question requires us first to get clear about what it means. There are some common confusions about truth that can get in the way of making progress toward explaining what it is. The purpose of this chapter is to clear away some of those confusions and to set the stage for the rest of the book.
1.1 Truth and the Truth
The question, ‘What is truth?’ strikes some people as one of the deepest and most elusive philosophical questions. Some people seem to think it is all but unanswerable. They might think knowing what truth is would mean knowing everything there is to know, or knowing the ultimate secrets of the universe – the explanations of everything puzzling, strange, surprising, wonderful, mysterious, or confusing in the world. Knowledge of the nature of truth then seems to be a kind of mystic wisdom that might be possible for gods and prophets, but not for us ordinary people.
Fortunately for philosophers interested in truth, that view is mistaken. It derives from a couple of different confusions. One is to confuse truth with the universe or reality as a whole. But truth is not the universe. It is a property had by the claim that chickens hatch from eggs and lacked by the claim that amphibians have fur. Explaining the nature of truth means explaining the nature of that property, not explaining the universe as a whole.
A second confusion that makes ‘What is truth?’ seem to require mystical insight is the idea that answering the question means knowing all the most important and fundamental things. This idea might confuse the question ‘What is truth?’ with the similar sounding question, ‘What is the truth?’.
Ordinarily, if you want to know the truth, you want to know the truth about something in particular. You want to know whether your romantic partner is faithful, or when the train is scheduled to depart, or how the new welfare policies will affect the economy. Unless you are asking about some topic that is already philosophical, ‘What is the truth?’ is not usually a philosophical question.
Sometimes, though, someone might ask what the truth is, and mean something very general. Such a person wants to know the truth about everything, either by knowing all there is know, or by knowing deep principles that explain everything there is to explain. This is probably impossible. We humans are incapable of omniscience, and there probably are no deep principles that explain absolutely everything, apart from the most fundamental laws of nature. Thus it might be impossible to answer the most general version of the question ‘What is the truth?’. But ‘What is truth?’ is a very different question. Its answer need not tell us everything there is to know, or enable us to understand everything there is to understand. All it needs to do is to explain a certain property that ‘2 + 2 = 4’ and ‘Canada is north of Mexico’ have in common but ‘Seven is an even number’ and ‘France is an island’ lack.
In asking ‘What is truth?’, we are asking the sort of ‘What is X?’ question Socrates was famous for pursuing. In Euthyphro, for example, he asks, “What is piety?” and he refuses to accept an answer that is just a list of pious acts. He wants an explanation of what makes acts pious or impious, not a list of examples. He wants to know what the nature of piety is. Likewise, when we ask what truth is, we are not interested in compiling a list of examples of true claims. We are not asking for the truth about some subject matter (apart from the truth about the nature of truth), and we are not asking for an explanation of the universe as a whole. We want to know what it means for a claim to be true or false. A good answer will explain what makes true claims true and false claims false, and it will thereby tell us about the nature of truth.
In Metaphysics, Aristotle says, “To say of what is not that it is, or of what is that it is not, is false, while to say of what is that is, and of what is not that it is not, is true.” This may not be a complete answer to the question, ‘What is truth?’, but it is a start. In particular, it helps to clarify the problem. We use the adjective ‘true’ in many different ways. We talk about true friends and false friends. A carpenter might describe a properly aligned beam as “true.” True diamonds are worth more than fakes. Elvis Costello released an album called My Aim is True, and the title is not nonsense. Although these notions of truth might have some family relation to what Aristotle was talking about, he was clearly concerned with something else. He was concerned with the notion of truth in the sense of accuracy, of getting it right about how things are. Asking what truth is, in this sense, is asking what it means for something to be accurate or get it right about how things are.
1.2 Truth Bearers
Before we can say much about what truth is, we need to have some idea about what sort of things are capable of being true or false, in the Aristotelian sense of getting it right or wrong about how things are. There are a lot of candidates, including sentences, propositions, utterances, statements, beliefs and theories. All of these things are “truth bearers,” which means they are the sorts of things that can be true or false. They all contrast with such things as mailboxes and marbles, which are not capable of being true or false in the relevant sense. Mailboxes and marbles are not truth bearers.
Among truth bearers, some might be more fundamental than others. Take utterances and sentences, for example. A sentence is a sequence of words that satisfies certain grammatical rules. An utterance is an event consisting of someone using a sentence. For example, Jack might say, “There is water in the well on Goose Hill at 7:00 p.m. local time, October 1, 2001,” and Jill might also say, “There is water in the well on Goose Hill at 7:00 p.m. local time, October 1, 2001.” Those are two utterances of the same sentence. If we already had an explanation of truth and falsity for sentences, we might be able to use it to explain truth and falsity of utterances: Utterances of true sentences are true, utterances of false sentences are false, and that's all there is to it. Such an explanation treats sentences as more fundamental truth bearers than utterances.
Philosophers disagree about what the most fundamental truth bearers are. Some think sentences are the most fundamental. Once we understand what it means for a sentence to be true, they think, we will be in a position to explain what it means for any other truth bearer to be true as well. Others think propositions are the most fundamental truth bearers.
A proposition, as philosophers use the term, is a certain kind of abstract object. The general idea is that a proposition is what is said when you say something and what is believed when you believe something. If Jill says, in English, “London is pretty,” and Jacques says, in French, “Londres est jolie,” there is a sense in which they have said the same thing. If you and I both believe that water is wet, there is a sense in which we believe the same thing. And if you tell me that there are potatoes in the pantry, and I believe you, there is a sense in which what I believe is what you said. Philosophers who believe in propositions think that, in order for a person to believe or say something, there must be a thing that the person believes or says. That thing is a proposition. Those who think of propositions as the fundamental truth bearers think that other truth bearers are made true (or false) by their relationships to true (or false) propositions. A belief is true when what is believed is a true proposition, for example, and an utterance is true when what is said is a true proposition.
Philosophical debates about the fundamental truth bearers can be very complicated. Sentences and propositions are the main candidates. Philosophers who think of sentences as the fundamental truth bearers often think it is metaphysically extravagant to believe in propositions. They might think so because they do not believe in any abstract objects, including numbers, properties, and propositions. Or they might think so because those who believe in propositions have been unable to give a clearly correct explanation of their so-called identity conditions – what it takes for two sentences to express the same proposition and what it takes for them to express different propositions. Philosophers who think of propositions as the fundamental truth bearers are often doubtful that anything else, including sentences, could have the features required to serve as properly fundamental truth bearers, and they sometimes claim that work in the philosophy of mind and the philosophy of language relying on the idea of propositions has been too fruitful and successful to discard.
This book will mostly ignore the debate about the fundamental truth bearers. Instead of taking a side, I will use the neutral term ‘claim’ to refer to the fundamental truth bearers, whatever they might be. Some theories, however, are expressly designed with sentences or propositions in mind as the fundamental truth bearers. When this choice makes a difference, it will be noted.
1.3 Being True and Being Taken to be True
Some people think that, when it comes down to it, there really isn't very much truth. Maybe even nothing is true. They might say, for example, that we really can't call claims about the relative positions of the earth and sun, the molecular structure of DNA, the events of the War of the Roses, or very much else true. We can't call them true because we cannot be certain of them, and, the reasoning goes, we must be certain of something before we can call it true. Some people might even take this line of thought further. They might point out that there is always room for some doubt; we can never be 100 percent certain of anything. And, since whatever is true is 100 percent certain, there really aren't any true claims. There are only more or less probable ones.
Other people take a much more permissive view. They are impressed by the idea that it is somehow improper to call what someone else believes very deeply untrue. On this view, whatever anyone believes is true. While the first view denies that anything is true, the second allows that everything is true, so long as someone believes it.
Both views are mistaken in a variety of ways. They have more sophisticated and plausible cousins that will be discussed in Chapter 2. But it is worth pausing here long enough to note a mistake the two views have in common. Each equates being true with being treated as true. According to the first view, we are rarely or never entitled to treat anything as true, and so nothing is true. According to the second view, we are rarely or never entitled to treat what someone believes as untrue, and so whatever anyone believes is true.
Of course, there is a great deal of difference between being true and being treated as true, just as there is a great deal of difference between being a criminal and being treated as a criminal. For a very long time, it was not at all certain that the earth was shaped more like a sphere than a pancake. Nevertheless, during that time, the earth was shaped more like a sphere than a pancake – it was true that the earth was shaped more like a sphere than a pancake. And no matter how deeply or sincerely I believe that there is another beer in the refrigerator, my believing does not make it true that one is there.
There are two important methodological points we can extract from the difference between being true and being taken to be true. First, we cannot hope to study truth the way we might study butterflies, by amassing a large collection of specimens and examining their similarities and differences. We might be able to make some progress in that way, but we could not make very much, because we do not have a guarantee that our specimens of truth are the genuine article. I might think something is true, but I could be mistaken. To study truth, then, we need to proceed more philosophically. We need to consider some plausible accounts of what truth might be, and we need to be clear about what we want a theory of truth to explain. Then we must proceed cautiously and tentatively, in hopes of finding a theory that does the work we need it to do.
Second, the failure of the idea that being true is being taken to be true can be used to illustrate an important philosophical tool for evaluating theories of truth. The following two claims might strike you as obviously correct:
In fact, almost any instance of the pattern ‘If _, then it is true that _.’ is correct when we fill both blanks with the same statement in English. If truth were the same as certainty, however, those same instances of the pattern ‘If _, then it is certain that _.’ would be correct as well. But they are not:
Both those claims could easily be false, even though the similar claims involving truth are true.
Another pattern whose instances are almost always correct is ‘If it is true that _, then _’ (assuming we fill in the blanks with the same statement in English, of course!). Two examples are:
And if truth were the same as being believed, then the corresponding instances of ‘If it is believed that _, then _’ would have to be correct as well:
Those two claims are obviously wrong, though.
The patterns ‘If _, then _ is true’, ‘If it is true that _, then _’, and their relatives have been very important in philosophical thinking about truth from the early twentieth century onward. One of the mathematician and philosopher Alfred Tarski's most influential contributions to our understanding of truth was a requirement he proposed for any theory of truth to be acceptable. An adequate theory of truth, he said, had to imply every instance of the pattern:
where ‘S’ is the name of a sentence and ‘s’ is replaced by a translation of that sentence into the language of the theory. For example, suppose we are formulating a theory of truth in English, and the theory is supposed to apply to sentences in English. (This would violate other requirements Tarski proposed, but it is good enough for our example.) And suppose we can make a name for a sentence by putting it in quotation marks. Then, given Tarski's requirement, our theory can be adequate only if it implies such things as:
and so on.
A “T-biconditional” is an instance of Tarski's pattern, ‘S is true if, and only if, s’ or a claim of the form ‘It is true that _, if, and only if, _’, with the two blanks filled in the same way. Although there are some problematic cases, such as ‘It is true that this sentence is false if, and only if, this sentence is false’, almost all the T-biconditionals are obviously true. A good theory of truth will, at the very least, be consistent with those T-biconditionals. Ideally, it will explain them. We can adopt the following principle for evaluating a theory of truth, which will be called the Equivalence Principle:
Except for those that involve paradoxes of some sort, T-biconditionals are true. An acceptable theory of truth must accommodate or explain that fact.
Sometimes this book will refer to “the Equivalence Schema.” The Equivalence Schema is the pattern the T-biconditionals fit, either ‘It is true that _ if, and only if, _’ or ‘S is true if, and only if, s.’
1.4 What Lies Ahead
The following two chapters consider a pair of problems that are closely tied to the question ‘What is truth?’ One is the problem of objectivity. Are there claims that are objectively, mind-independently true, or does truth depend in some way on what we think or what we could think? The other is the problem of the value of truth. In what sense are true beliefs or assertions “better” than false ones? Just as a good theory of truth will satisfy the Equivalence Principle, a good theory of truth would also provide a good understanding of objectivity and explain the value of truth. The various approaches to explaining the nature of truth that Chapters 4 through 7 explore have different commitments with respect to objectivity and value, and one way of evaluating them is to consider what those commitments are.
Further Reading
Several of Plato's dialogues deal with the difference between explaining the nature of something and listing examples. Among them are Euthyphro, Meno, and the Republic, which also contains a great deal of interesting discussion of the relationship of truth to knowledge.
Aristotle's views on truth are scattered through several of his works, especially the Metaphysics and the Posterior Analytics. In Metaphysics Book IV (Γ), Chapter 8, Aristotle argues against the views that nothing is true and that everything is true on the grounds that they are self-defeating: If nothing is true, then neither is the doctrine that nothing is true; and if everything is true, then so is the doctrine that not everything is true.
Wolfgang Künne's book, Conceptions of Truth (2003), includes excellent discussions of a wide range of issues, including the issue of fundamental truth bearers in its fifth chapter. The roots of the modern conception of a proposition lie in Gottlob Frege's important essay, “The Thought” (1956). The second chapter of W. V. Quine's classic, Word and Object (1960), argues that there is usually not a determinate fact of the matter what a person's utterances mean, which would imply that there is no determinate fact of the matter whether two people have said the same thing or expressed the same proposition. A pair of papers by Hartry Field, “Mental Representation” and “Deflationist Theories of Meaning and Content,” make the case for dispensing with propositions in our understanding of belief and truth. They are both reprinted in the collection, Truth and the Absence of Fact (Field 2001).
Alfred Tarski's “The Semantic Conception of Truth and the Foundations of Semantics” (1944) both sets out the requirement that a good theory of truth should imply the T-biconditionals and contains a treatment of the logic of the expression ‘_ is true’ that has been absolutely central to future logical work on truth and the paradoxes of truth (such as the paradox posed by the sentence, ‘This sentence is false’).
2
Objectivity
People sometimes wonder about the nature of truth because they are interested in the question whether anything is “objectively” true. Does the truth depend on what people, or the right people, believe? Or are there some claims that are true regardless of what anyone thinks? One idea of an “objective” truth is the idea of a claim whose truth or falsehood does not depend on what anyone believes.
A second set of questions also falls under the heading of objectivity. Those questions concern the relationship between truth and knowledge. Sometimes we can tell whether a claim is true or false, and sometimes it is impossible for us to know one way or the other. If there is no way to tell whether a claim is true or false, can it even be true or false? One idea of “objective” truth is the idea that the truth of a claim does not depend on whether or not we could know it. There could be claims that are true but unknowable. According to some philosophers, though, the idea of an unknowable truth is nonsense. On their view, if it is impossible to know whether something is the case, then there simply is no fact of the matter either way. These philosophers thus think of the limits of possible knowledge as the limits of truth and, in that sense, the limits of reality
This chapter concerns the three-way debate over objectivity. On one side is realism, the view that there are some claims whose truth does not depend on their being believed by anyone or even on the possibility of anyone's knowing them. On another side is relativism, the view that the truth is always a matter of opinion, in the sense that the truth of any claim always depends on who believes it. The third contender is anti-realism, the view that part of what makes a claim true is the fact that we can know it, and so claims we cannot know to be true or false cannot be true or false. Each view presents a different picture of how the world is, and each has its own advantages and disadvantages. This chapter discusses those advantages and disadvantages, with the upshot that a mild form of realism is the most plausible of these views.
2.1 Three Pictures of Reality
Realism, anti-realism, and relativism present different views of the world and its relationship to our minds. Realists take the commonsense view that there is a world “out there,” and the facts are as they are irrespective of what anyone thinks about them. There are some claims that would be true even if no one believed them, or false even if everyone did. Moreover, although we may be able to acquire some knowledge about the mind-independent world, claims are ordinarily knowable because they are true, not true because they are knowable. What makes a claim true need not have anything to do with the possibility of knowing it. Realists might disagree with each other about which parts of reality are mind-independent, but they agree that something is.
Astrophysicists say parts of the universe more than about 62 billion light years away are too distant for any information from there to reach us – ever (Gott et al. 2005). Consider the claim (whose truth we could not possibly know) that there are an odd number of water molecules exactly 63 billion light years from Earth. A realist is apt to say that, regardless of whether anyone believes or disbelieves that claim, and despite the fact that we have no way of knowing one way or the other, the claim is either true or false. Either there are an odd number of water molecules 63 billion miles away, or there are not.
Relativists think of the world as made up, like a story. Truth and falsehood depend on what people believe. And just as there is no such thing as absolute “to the leftness,” but only being to the left of something, there is no such thing as absolute truth, only truth for someone. A table might be to the left of the window but not of the stove, and a claim might be true for one person but false for another. Belief is what makes the difference. On the relativist view, what makes a claim true for someone is that they believe it, and what makes it false for someone is that they disbelieve it.
Suppose Jill has told a joke. Maybe some people think it is funny and some people think it isn't. It's very tempting to think the joke is funny for those who think it is, but it isn't funny for those think it isn't. It's also tempting to think that is all there is to it. There is no underlying fact about whether the joke is “really” funny or not, because part of what it means for something to be funny is for people to think it's funny. Relativists think all claims are like the claim that Jill's joke is funny. Not only the truth about funniness, but all truth depends on what people believe, and it is always someone's truth. What a person believes is true for her; what she disbelieves is false for her; and where she has no opinion, there is neither truth nor falsehood.
Anti-realists do not think truth depends on belief, and they do not think that all truth is someone's truth. But they do think truth is mind-dependent in another way. According to anti-realists, a claim cannot be true unless it is possible to find out or know it is true. Likewise, a claim cannot be false unless it is possible to find out or know it is false. If there is no way to know that a claim is true, anti-realists think, then that claim must not be true – it must either be false or have no truth value at all. On the anti-realist view, the concepts of truth and knowability are tightly linked because part of what it means for a claim to be true is that there is a way we could find out that it's true. This makes truth mind-dependent because the limits of possible knowledge are also the limits of reality. If there is no way to find out whether there are an even or odd number of water molecules exactly 63 billion light years from earth, then there is no fact of the matter about it. It's neither true nor false that there is an even number, and it's neither true nor false that there is an odd number. Instead, the question represents a gap in reality.
There are thus two big questions to be addressed in the debate among realists, relativists, and anti-realists. First, is anything true irrespective of what anyone believes? If so, then relativism is incorrect. Second, is there anything that is true even though there is no way, in principle, for anyone to know that it is? If so, then anti-realism is incorrect.
2.2 Realism
The realist picture of reality draws on two important aspects of our experience. First, we sometimes find that we have mistakenly believed something that was not true. Second, we sometimes discover truths we were unaware of before. These experiences allow us to distinguish between how things really are and what we happen to believe. A natural way to make that distinction is to think of the world as “out there” and independent of us. The world is a collection of objects or facts that are as they are regardless of what we think, and even regardless of what we could believe or know.
Consider, for example, the claim that the earth is shaped more like a sphere than a pancake. People used to disbelieve that claim, but they later discovered that they were mistaken. They discovered that things were not as they thought they were. But what if there had been no way for anyone to know the shape of the earth? What if no intelligent life had ever existed in the universe? Still, we tend to think, the earth would have been shaped more like a sphere than a pancake. The shape of the earth is supposed to be exactly the sort of thing that is indifferent to what we happen to believe, or even to what it is possible to know.
One of the greatest appeals of realism is its explanatory power. Realism explains why it is possible for beliefs to be mistaken. For example, it is possible for a belief about the shape of the earth to be mistaken because the shape of the earth does not depend on what anyone thinks about it. Realism also provides a way to make sense of what happens when we discover something new. There are facts that are out there, independent of us, that we have not yet come to know. Discoveries happen when we find a way to know them.
But realism goes further than that. Not only does it say there are claims whose truth does not depend on our believing them, but it says there are claims whose truth does not depend on the possibility that we could know them. Why should we think there are such facts?
One reason applies what we already know about the world. What makes it true that the earth is round, for example, appears to be something about the earth itself, not its relationship to intelligent life. After all, it was true long before there were any intelligent beings to know it, and it would have been true even if those intelligent beings had never existed. Given what we know about the world, then, there seem to be some claims whose truth does not require the possibility of their being known.
Another reason has to do with the fact that there are some claims whose truth or falsity we cannot know. Consider the claim that the last dinosaur chipped a tooth ten minutes before dying. We have no way of finding out whether that claim is true or false. However, it is natural to suppose that the dinosaur either did or did not chip a tooth ten minutes before dying. Either way, then, there is something that is true but impossible to know.
The realist conception of the world might seem appealing to common sense, but it does face some difficulties. One objection to realism is that, if there were any objectively true claims, it would be impossible to know whether those claims were true or false. According to this objection, realism makes knowledge of the mind-independent world impossible. The view that such knowledge is impossible is called “skepticism,” and this objection raises the problem of skepticism for realism.
Why think realism entails skepticism? The idea is that all our knowledge ultimately derives from how things seem to us, and from no other source. “How things seem” includes our perceptual experiences, and it may also include so-called “intellectual seemings,” which occur when you think about a claim and it strikes you as true or as false, regardless of your sensory experiences. For example, think about the claim that murder is wrong and the claim that 1 + 1 = 11. The former claim probably seems true to you, and the latter probably seems false. Those are intellectual seemings.
Given realism, though, how the world is could be radically different from how it seems to be. A classic example in this vein is René Descartes' (1641) thought experiment involving a deceptive demon. We have no way to rule out the possibility we are the victims of a demon who has arranged for everything to seem to us as it does, even though the physical world does not exist at all. In that case, all our beliefs about the external world would be false. It would seem to us that there are tables and chairs, that there used to be dinosaurs, that objects in motion tend to stay in motion, and even that there are infinitely many prime numbers, but all those appearances are due to the demon's deceptions. Things could seem that way without any of those claims being true.
According to this objection to realism, if how things are is independent of how they seem, demon-like deception is possible. We have no way to rule it out. And since we have no way to rule it out, we cannot know whether the external world exists or, instead, is all an illusion. We cannot really know anything about the external world unless we can rule out such possibilities, and so, the objection goes, realism entails skepticism.
Realists have responded to the skeptical problem in several ways. According to Descartes, we can know that God exists, and this guarantees that how things seem is a reliable guide to how they mind-independently are. After all, God is perfectly good, and a perfectly good God would not allow us to be radically misled by how things seem. Descartes' solution does not work, though. The existence of God is precisely the sort of thing realists think of as mind-independent, and its seeming that God exists is no guarantee that he really does. Even if God didn't exist, the demon could make it seem as though he did.
