The Proof

Uses of Evidence in Law, Politics, and Everything Else

Frederick Schauer

• Publisher: Belknap Press
• Year: 2022
• ISBN:
  9780674276253
• Topic: Law
• Subtopic: Law Theory & Practice
• Index: Law

Winner of the Scribes Book Award "Displays a level of intellectual honesty one rarely encounters these days…This is delightful stuff."
—Barton Swaim, Wall Street Journal "At a time when the concept of truth itself is in trouble, this lively and accessible account provides vivid and deep analysis of the practices addressing what is reliably true in law, science, history, and ordinary life. The Proof offers both timely and enduring insights."
—Martha Minow, former Dean of Harvard Law School"His essential argument is that in assessing evidence, we need, first of all, to recognize that evidence comes in degrees…and that probability, the likelihood that the evidence or testimony is accurate, matters."
—Steven Mintz, Inside Higher Education "I would make Proof one of a handful of books that all incoming law students should read…Essential and timely."
—Emily R. D. Murphy, Law and Society Review In the age of fake news, trust and truth are hard to come by. Blatantly and shamelessly, public figures deceive us by abusing what sounds like evidence. To help us navigate this polarized world awash in misinformation, preeminent legal theorist Frederick Schauer proposes a much-needed corrective.How we know what we think we know is largely a matter of how we weigh the evidence. But evidence is no simple thing. Law, science, public and private decision making—all rely on different standards of evidence. From vaccine and food safety to claims of election fraud, the reliability of experts and eyewitnesses to climate science, The Proof develops fresh insights into the challenge of reaching the truth. Schauer reveals how to reason more effectively in everyday life, shows why people often reason poorly, and makes the case that evidence is not just a matter of legal rules, it is the cornerstone of judgment.

Chapter 1As a Matter of Fact

ELVIS IS DEAD. Tabloid headlines to the contrary, Elvis Presley really did die on August 16, 1977, and he has remained dead ever since.

For purposes of this book, the importance of Elvis’s death is that it is a fact. And as a fact, its existence is distinct from people’s personal or policy preferences. As we will see, even issues as seemingly straightforward as the death of Elvis are not nearly so simple, but it is still crucial at the outset to distinguish the fact of Elvis’s death from the preferences of many people that he be alive and perhaps even the preferences of some people that he be dead. Such preferences exist apart from the fact that Elvis is dead.¹

For all its triviality, the Elvis example highlights three important distinctions about the place of facts both in public policy and in personal decision making. First is this distinction between the empirical reality and what some or many people prefer or wish that empirical reality to be. Disliking anchovies is a preference. Believing that anchovies do not exist is an empirical mistake. And taking a dislike for anchovies as a reason for denying their empirical existence is a fallacy.

The second important distinction is between actual empirical reality and what some or many people believe that empirical reality to be. It is a fact that vaccination does not cause autism, even though many people believe otherwise.² It is a fact that the earth is warming, although some people and political parties are committed to denying that fact. And recently, and to some extent still, major government policies regarding public expenditures, regulation of businesses, and personal freedom have turned on whether the rates of incidence, hospitalization, and death from Covid-19 are rising, falling, or disappearing. But these rates, whatever they are, are facts. So are conclusions about whether these rates are higher than, lower than, or the same as they were a month ago, at least assuming a common scale of measurement. Accordingly, when a president or anyone else asserts that the rate is lower than it was at some time in the past, we can check the assertion against the facts. And we can also investigate whether some drug—such as hydroxychloroquine, whose effectiveness was often and erroneously touted in the early days of the Covid-19 pandemic—is or is not effective against Covid-19 and whether it does or does not cause side effects of a certain type.³ These are facts, and they exist apart from whatever may be asserted by a president, the Centers for Disease Control and Prevention, or anyone else.

The Covid-19 pandemic highlights the third important distinction—the distinction between (a) what the facts are and (b) what ought to be done about them. Describing the world and prescribing policy are two different things. The fact that the rate of Covid-19 infection is falling, whenever it is in fact falling, does not itself tell government whether to relax restrictions that are in place, nor does that fact tell people whether to start eating in restaurants, participating in live political rallies, or attending church services. And the fact that rates of infection are rising, whenever that is the fact, does not itself tell universities to cease holding in-person classes or advise individuals to stop taking public transportation. All these decisions about what to do are based on facts, but they require something more than facts alone. It is wise—indeed essential—to follow the science, and thus to follow the facts, in making policy and personal decisions. But following the facts and following the science means basing policies on actual facts—and not incorrect factual beliefs or “alternative facts.” It means using rather than contradicting what the science tells us. But following the facts and following the science does not, and cannot, mean—despite occasional pronouncements by scientists and government officials to the contrary—that science and facts alone can determine what some policy ought to be. Making policy decisions requires using the facts to reach what are irreducibly normative and value-laden conclusions. And these policy decisions usually require trade-offs whose resolution cannot be determined solely by the facts. What to do about the facts is not solely a factual inquiry, just as what to do with science is not solely a scientific task. However important it is to follow the science and follow the facts, it is also important to recognize that science, and the facts, can only take us so far.

Facts alone cannot indicate what people or governments should do, but facts remain the foundation for sound public and personal decision making. In memorably remarking that people are entitled to their own opinions but not their own facts, the late senator Daniel Patrick Moynihan reminded us that making correct decisions depends on getting the facts right.⁴ As he put it on the same occasion, “First, get your facts straight.” And although Moynihan was talking largely about governmental policy decisions, questions of fact provide the basis for many of the more personal decisions we make on a daily basis. Some people, for example, refuse to patronize establishments owned by members of the Ku Klux Klan or by others who hold racist or other opinions that the potential customers abhor. But the initial question facing the potential customer is whether the proprietor is or is not a Klan member, or does or does not harbor racist views. These are questions of fact, and they are part of our everyday lives. It may (or may not) be a morally good thing to refuse to patronize a shop whose owner is a member of the Klan, but it is plainly not a morally good thing to refuse to patronize a shop on the belief that the owner is a Klan member if in fact he is not. Our lives and our decisions involve numerous choices that are driven by values—normative political or moral or personal preferences. But acting on those preferences requires making an initial judgment that is factual and not normative. Doing the right thing matters, but getting the facts right is the first step.

The forgoing is obvious to the point of banality, but highlighting the increasingly common questions about what is—and not just about what we or some government ought to do—is the appropriate entry into what this book is all about. More than two centuries ago the philosopher David Hume warned against the fallacy of deriving “ought” from “is”—of moving from the descriptive to the normative, or from what is to what ought to be—without recognizing that the move requires judgments that cannot be based on facts alone.⁵ But it is no less a fallacy to attempt to derive “is” from “ought.” It would be nice if there were world peace and nonfat bacon, but wishing won’t make it so. This book is based on the premise that controversies about facts are important in their own right, but even more so because they provide the foundations for questions of personal choice and public policy. Leaving to others questions about how we or government ought to act, this book is an attempt to provide some insight into how we do—and, yes, should—confront the factual questions and controversies that are all around us.

The Idea of Evidence

It is one thing to say that there are facts; it is quite another to determine what those facts are. And once we shift from the idea of a fact to questions about figuring out what those facts are—to deciding which claims about the facts are true and which are false—we enter the realm of evidence, the subject of this book. Evidence is what provides the justification, or warrant, as philosophers are prone to put it, for believing that something is true—or false. Pieces of evidence are facts, but they are the facts that lead us to the conclusion that other facts do or do not exist. The fact that the skin tone and whites of someone’s eyes appear yellowish is evidence for the further fact that the person has hepatitis.⁶ The fact that the engine on my car is making a pinging sound is evidence for the fact that the gasoline in the tank is of too-low octane. The fact that Herman’s fingerprints are on the door handle of Susan’s stolen car is evidence for the fact that Herman was the thief. And the fact that then-nominee and now Supreme Court Justice Amy Coney Barrett signed an anti-abortion advertisement some years ago is evidence for what she then believed, which is in turn evidence for what she now believes, which is in turn evidence for how she might now decide.⁷

This book deals only indirectly with what makes a fact a fact, and with what makes a true statement true and a false one false. But it deals directly with how we know that statements or conclusions are true or false. In philosophical terminology, the focus of this book is on epistemology and not ontology (or metaphysics). In everyday language, the book is not about what is or what is not. It is about how we determine what is, and how we know what is not. It is about the assessment of factual truth and falsity in public policy, in public deliberation, and in personal decision making.

The Demand for Truth

Evidence is the prerequisite for judgments of truth (and falsity). But as we will see in Chapter 13, what psychologists call “motivated reasoning” is a large part of the evidentiary terrain. Unfortunately, how people perceive the facts of the world is often substantially influenced by their normative preferences about how they would like the world to be. It is a question of fact—in theory verifiable—whether the soccer ball crossed the line into the goal, but supporters of the team that kicked the ball will almost invariably believe in close cases that the ball crossed the line, just as supporters of the defending team will equally invariably believe that it did not. Although the location of President Barack Obama’s birth is a question of fact, it comes as no surprise that his supporters believed (correctly) that he was born in Hawaii, just as many of his political opponents believed (falsely) that he was born in Kenya. And when asked who “won” a debate between candidates for president, a question whose answer is admittedly far less factual and far less verifiable, it is still noteworthy that both prospective voters and pundits reach conclusions that are expectedly and tediously consistent with their political preferences.⁸ So too, as in recent events, with a closely contested election, where again many people’s assessments of the facts align all too conveniently with their political and outcome preferences.⁹

Even more fundamentally, however, evidence matters only to those for whom truth matters. And it is not clear that truth matters to everyone, in the same contexts, and to the same degree. If we think of truth as something that can be preferred (or not), we can then understand a preference for truth as competing with preferences for happiness, affection, friendship, ambition, wealth, health, lack of stress, and a myriad of other emotions and conditions that may at times conflict with and be more important to some people than truth. Although Henry Clay was talking more about policy than fact when he observed in 1839 that he would rather be right than president, his observation has endured precisely because we recognize that many (most?) politicians would rather be president than right.¹⁰ Being right is a preference for the truth, but not everyone has that preference, or has it in the same amount, or has it all the time.

If truth is a preference, then we should recognize that there can be a market for truth. Suppliers of truth, and thus suppliers of evidence, will understand that not everyone wants evidence, or wants it to the same degree. And if this conclusion seems uncomfortable, it is not uncomfortable for the publishers of supermarket tabloids. Many people enjoy reading about the travails of the rich and the famous, producing a demand for information—the more detailed the better—about these travails. And the suppliers of information about such travails, the supermarket tabloids prominently among them, seek to satisfy the demand, whether the travails actually exist or not. Obviously at some point stories about the misfortunes and missteps of the rich and famous will be so untethered from reality—from the evidence—that the demand will contract. And equally obviously, at some point the reality will be sufficiently uninteresting that the demand will again contract. The successful publishers of sensationalist supermarket tabloids are those who can best assess this relationship between the demand for sensationalism and the demand for truth. These financially successful tabloid publishers have located the optimal equilibrium—the point beyond which more truth (and thus more evidence) will decrease demand for the information, and the point beyond which less sensationalism will also decrease the demand for the information. Success in the tabloid business depends on discovering whatever balance between sensation and truth maximizes readership (and thus sales and advertising revenue).

This is not a book about the publishing industry, whether tabloid publishing or academic publishing or anything in between. But this detour into tabloid publishing illustrates that it is hardly obvious—as if recent events were not enough to make the point—that more truth (or more knowledge) is equally important for all people (or institutions) at all times and for all subjects. And it is equally not obvious that evidence, the basis for our knowledge and the basis for our judgments of truth and falsity, is equally important for all people at all times and for all subjects. This book is about evidence, and is premised on the idea that evidence is often important because truth is often important. But understanding the place of evidence in the world, in public policy, and in personal decision making requires understanding that evidence and truth are not the only values there are.

Of Facts and Opinions

It is a fact that Adolph Hitler had a mustache, and it is a fact that he was born in Braunau am Inn, Austria, on April 20, 1889. It is also a fact that he was evil, but this latter fact, unlike the others, is evaluative. It involves a judgment, or what some would call an “opinion.” In this case the judgment is easy, and few people, or at least few with whom I associate, would dissent from characterizing Hitler as evil. Frequently, however, the evaluation is less obvious and more contested. And often, and even more of a problem, the evaluation hides within a seemingly factual statement. The philosopher Philippa Foot gave us the idea of a “th...