The CDA prompted massive protests (and litigation) charging the government with censorship. The Supreme Court agreed in the landmark case of Reno v. ACLU (1997), which struck down the CDA’s decency provisions. In his opinion for the Court, Justice John Paul Stevens explained that regulating the content of Internet expression is no different from regulating the content of newspapers.The case is arguably the most significant free speech decision over the past half century since it expanded the full protection of the First Amendment to Internet expression, rather than treating the Internet like television or radio, whose content may be regulated more extensively. In language that might sound dated, Justice Stevens announced a principle that has endured: “Through the use of chat rooms, any person with a phone line can become a town crier with a voice that resonates farther than it could from any soapbox. Through the use of web pages, mail exploders, and newsgroups, the same individual can become a pamphleteer.” The Internet, in other words, was now an essential forum for free speech.

In the aftermath of Reno, Congress gave up on policing Internet indecency, but continued to focus on child protection. In 1998 it passed the Children’s Online Protection Act, also known as COPA. COPA punished those who engaged in web communications made “for commercial purposes” that were accessible and “harmful to minors” with a $50,000 fine and prison terms of up to six months. After extensive litigation, the Supreme Court in Ashcroft v. ACLU (2004) upheld a preliminary injunction preventing the government from enforcing the law. The Court reasoned that the government hadn’t proved that an outright ban of “harmful to minors” material was necessary. It suggested that Congress could have instead required the use of blocking or filtering software, which would have had less of an impact on free speech than a ban, and it remanded the case for further proceedings. Back in the lower court, the government wanted to create a study showing that filtering would be ineffective, which is why it wanted the search queries from Google and the other search engine companies in 2006.

Judge James Ware ruled on the subpoena on March 17, 2006, and denied most of the government’s demands. He granted the release of only 5 percent of the requested randomly selected anonymous search results and none of the actual search queries. Much of the reason for approving only a tiny sample of the de-identified search requests had to do with privacy. Google had not made a direct privacy argument, on the grounds that de-identified search queries were not “personal information,” but it argued that disclosure of the records would expose its trade secrets and harm its goodwill from users who believed that their searches were confidential. Judge Ware accepted this oddly phrased privacy claim, and added one of his own that Google had missed. The judge explained that Google users have a privacy interest in the confidentiality of their searches because a user’s identity could be reconstructed from their queries and because disclosure of such queries could lead to embarrassment (searches for, e.g., pornography or abortions) or criminal liability (searches for, e.g., “bomb placement white house”). He also placed the list of disclosed website addresses under a protective order to safeguard Google’s trade secrets.

Two facets of Judge Ware’s short opinion in the “Search Subpoena Case” are noteworthy. First, the judge was quite correct that even search requests that have had their user’s identities removed are not anonymous, as it is surprisingly easy to re-identify this kind of data. The queries we enter into search engines like Google often unwittingly reveal our identities. Most commonly, we search our own names, out of vanity, curiosity, or to discover if there are false or embarrassing facts or images of us online. But other parts of our searches can reveal our identities as well. A few months after the Search Subpoena Case, AOL made public twenty million search queries from 650,000 users of its search engine users. AOL was hoping this disclosure would help researchers and had replaced its users’ names with numerical IDs to protect their privacy. But two New York Times reporters showed just how easy it could be to re-identify them. They tracked down AOL user number 4417749 and identified her as Thelma Arnold, a sixty-two-year old widow in Lilburn, Georgia. Thelma had made hundreds of searches including “numb fingers,” “60 single men,” and “dog that urinates on everything.” The New York Times reporters used old-fashioned investigative techniques, but modern sophisticated computer science tools make re-identification of such information even easier. One such technique allowed computer scientists to re-identify users in the Netflix movie-watching database, which that company made public to researchers in 2006.

The second interesting facet of the Search Subpoena Case is its theory of privacy. Google won because the disclosure threatened its trade secrets (a commercial privacy, of sorts) and its business goodwill (which relied on its users believing that their searches were private). Judge Ware suggested that a more direct kind of user privacy was at stake, but was not specific beyond some generalized fear of embarrassment (echoing the old theory of tort privacy) or criminal prosecution (evoking the “reasonable expectation of privacy” theme from criminal law). Most people no doubt have an intuitive sense that their Internet searches are “private,” but neither our intuitions nor the Search Subpoena Case tell us why. This is a common problem in discussions of privacy. We often use the word “privacy” without being clear about what we mean or why it matters. We can do better.

Internet searches implicate our intellectual privacy. We use tools like Google Search to make sense of the world, and intellectual privacy is needed when we are making sense of the world. Our curiosity is essential, and it should be unfettered. As I’ll show in this chapter, search queries implicate a special kind of intellectual privacy, which is the freedom of thought.

Freedom of thought and belief is the core of our intellectual privacy. This freedom is the defining characteristic of a free society and our most cherished civil liberty. This right encompasses the range of thoughts and beliefs that a person might hold or develop, dealing with matters that are trivial and important, secular and profane. And it protects the individual’s thoughts from scrutiny or coercion by anyone, whether a government official or a private actor such as an employer, a friend, or a spouse. At the level of law, if there is any constitutional right that is absolute, it is this one, which is the precondition for other political and religious rights guaranteed by the Western tradition. Yet curiously, although freedom of thought is widely regarded as our most important civil liberty, it has not been protected in our law as much as other rights, in part because it has been very difficult for the state or others to monitor thoughts and beliefs even if they wanted to.

Freedom of Thought and Intellectual Privacy

In 1913 the eminent Anglo-Irish historian J. B. Bury published A History of Freedom of Thought, in which he surveyed the importance of freedom of thought in the Western tradition, from the ancient Greeks to the twentieth century. According to Bury, the conclusion that individuals should have an absolute right to their beliefs free of state or other forms of coercion “is the most important ever reached by men.” Bury was not the only scholar to have observed that freedom of thought (or belief, or conscience) is at the core of Western civil liberties. Recognitions of this sort are commonplace and have been made by many of our greatest minds. René Descartes’s maxim, “I think, therefore I am,” identifies the power of individual thought at the core of our existence. John Milton praised in Areopagitica “the liberty to know, to utter, and to argue freely according to conscience, above all [other] liberties.”

In the nineteenth century, John Stuart Mill developed a broad notion of freedom of thought as an essential element of his theory of human liberty, which comprised “the inward domain of consciousness; demanding liberty of conscience, in the most comprehensive sense; liberty of thought and feeling; absolute freedom of opinion and sentiment on all subjects, practical or speculative, scientific, moral, or theological.” In Mill’s view, free thought was inextricably linked to and mutually dependent upon free speech, with the two concepts being a part of a broader idea of political liberty. Moreover, Mill recognized that private parties as well as the state could chill free expression and thought.

Law in Britain and America has embraced the central importance of free thought as the civil liberty on which all others depend. But it was not always so. People who cannot think for themselves, after all, are incapable of self-government. In the Middle Ages, the crime of “constructive treason” outlawed “imagining the death of the king” as a crime that was punishable by death. Thomas Jefferson later reflected that this crime “had drawn the Blood of the best and honestest Men in the Kingdom.” The impulse for political uniformity was related to the impulse for religious uniformity, whose story is one of martyrdom and burnings of the stake. As Supreme Court Justice William O. Douglas put it in 1963:

While kings were fearful of treason, theologians were bent on stamping out heresy. . . . The Reformation is associated with Martin Luther. But prior to him it broke out many times only to be crushed. When in time the Protestants gained control, they tried to crush the Catholics; and when the Catholics gained the upper hand, they ferreted out the Protestants. Many devices were used. Heretical books were destroyed and heretics were burned at the stake or banished. The rack, the thumbscrew, the wheel on which men were stretched, these were part of the paraphernalia.

Thankfully, the excesses of such a dangerous government power were recognized over the centuries, and thought crimes were abolished. Thus, William Blackstone’s influential Commentaries stressed the importance of the common law protection for the freedom of thought and inquiry, even under a system that allowed subsequent punishment for seditious and other kinds of dangerous speech. Blackstone explained that:

Neither is any restraint hereby laid upon freedom of thought or inquiry: liberty of private sentiment is still left; the disseminating, or making public, of bad sentiments, destructive of the ends of society, is the crime which society corrects. A man (says a fine writer on this subject) may be allowed to keep poisons in his closet, but not publicly to vend them as cordials.

Even during a time when English law allowed civil and criminal punishment for many kinds of speech that would be protected today, including blasphemy, obscenity, seditious libel, and vocal criticism of the government, jurists recognized the importance of free thought and gave it special, separate protection in both the legal and cultural traditions.

The poisons metaphor Blackstone used, for example, was adapted from Jonathan Swift’s Gulliver’s Travels, from a line that the King of Brobdingnag delivers to Gulliver. Blackstone’s treatment of freedom of thought was itself adopted by Joseph Story in his own Commentaries, the leading American treatise on constitutional law in the early Republic. Thomas Jefferson and James Madison also embraced freedom of thought. Jefferson’s famous Virginia Statute for Religious Freedom enshrined religious liberty around the declaration that “Almighty God hath created the mind free,” and James Madison forcefully called for freedom of thought and conscience in his Memorial and Remonstrance Against Religious Assessments.

Freedom of thought thus came to be protected directly as a prohibition on state coercion of truth or belief. It was one of a handful of rights protected by the original Constitution even before the ratification of the Bill of Rights. Article VI provides that “state and federal legislators, as well as officers of the United States, shall be bound by oath or affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States.” This provision, known as the “religious test clause,” ensured that religious orthodoxy could not be imposed as a requirement for governance, a further protection of the freedom of thought (or, in this case, its closely related cousin, the freedom of conscience). The Constitution also gives special protection against the crime of treason, by defining it to exclude thought crimes and providing special evidentiary protections:

Treason against the United States, shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort. No person shall be convicted of treason unless on the testimony of two witnesses to the same overt act, or on confession in open court.

By eliminating religious tests and by defining the crime of treason as one of guilty actions rather than merely guilty minds, the Constitution was thus steadfastly part of the tradition giving exceptional protection to the freedom of thought.

Nevertheless, even when governments could not directly coerce the uniformity of beliefs, a person’s thoughts remained relevant to both law and social control. A person’s thoughts could reveal political or religious disloyalty, or they could be relevant to a defendant’s mental state in committing a crime or other legal wrong. And while thoughts could not be revealed directly, they could be discovered by indirect means. For example, thoughts could be inferred either from a person’s testimony or confessions, or by access to their papers and diaries. But both the English common law and the American Bill of Rights came to protect against these intrusions into the freedom of the mind as well.

The most direct way to obtain knowledge about a person’s thoughts would be to haul him before a magistrate as a witness and ask him under penalty of law. The English ecclesiastical courts used the “oath ex officio” for precisely this purpose. But as historian Leonard Levy has explained, this practice came under assault in Britain as invading the freedom of thought and belief. As the eminent jurist Lord Coke later declared, “no free man should be compelled to answer for his secret thoughts and opinions.” The practice of the oath was ultimately abolished in England in the cases of John Lilburne and John Entick, men who were political dissidents rather than religious heretics.

In the new United States, the Fifth Amendment guarantee that “No person . . . shall be compelled in any criminal case to be a witness against himself ” can also be seen as a resounding rejection of this sort of practice in favor of the freedom of thought. Law of course evolves, and current Fifth Amendment doctrine focuses on the consequences of a confession rather than on mental privacy, but the origins of the Fifth Amendment are part of a broad commitment to freedom of thought that runs through our law. The late criminal law scholar William Stuntz has shown that this tradition was not merely a procedural protection for all, but a substantive limitation on the power of the state to force its enemies to reveal their unpopular or heretical thoughts. As he put the point colorfully, “[i]t is no coincidence that the privilege’s origins read like a catalogue of religious and political persecution.”

Another way to obtain a person’s thoughts would be by reading their diaries or other papers. Consider the Fourth Amendment, which protects a person from unreasonable searches and seizures by the police:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Today we think about the Fourth Amendment as providing protection for the home and the person chiefly against unreasonable searches for contraband like guns or drugs. But the Fourth Amendment’s origins come not from drug cases but as a bulwark against intellectual surveillance by the state. In the eighteenth century, the English Crown had sought to quash political and religious dissent through the use of “general warrants,” legal documents that gave agents of the Crown the authority to search the homes of suspected dissidents for incriminating papers.

Perhaps the most infamous dissident of the time was John Wilkes. Wilkes was a progressive critic of Crown policy and a political rogue whose public tribulations, wit, and famed personal ugliness made him a celebrity throughout the English-speaking world. Wilkes was the editor of a progressive newspaper, the North Briton, a member of Parliament, and an outspoken critic of government policy. He was deeply critical of the 1763 Treaty of Paris ending the Seven Years War with France, a conflict known in North America as the French and Indian War. Wilkes’s damning articles angered King George, who ordered the arrest of Wilkes and his co-publishers of the North Briton, authorizing general warrants to search their papers for evidence of treason and sedition. The government ransacked numerous private homes and printers’ shops, scrutinizing personal papers for any signs of incriminating evidence. In all, forty-nine people were arrested, and Wilkes himself was charged with seditious libel, prompting a long and inconclusive legal battle of suits and countersuits.

By taking a stand against the king and intrusive searches, Wilkes became a cause célèbre among Britons at home and in the colonies. This was particularly true for many American colonists, whose own objections to British tax policy following the Treaty of Paris culminated in the American Revolution. The rebellious colonists drew from the Wilkes case the importance of political dissent as well as the need to protect dissenting citizens from unreasonable (and politically motivated) searches and seizures.

The Fourth Amendment was intended to address this problem by inscribing legal protection for “persons, houses, papers, and effects” into the Bill of Rights. A government that could not search the homes and read the papers of its citizens would be less able to engage in intellectual tyranny and enforce intellectual orthodoxy. In a pre-electronic world, the Fourth Amendment kept out the state, while trespass and other property laws kept private parties out of our homes, paper, and effects.

The Fourth and Fifth Amendments thus protect the freedom of thought at their core. As Stuntz explains, the early English cases estab- lishing these principles were “classic First Amendment cases in a system with no First Amendment.” Even in a legal regime without protection for dissidents who expressed unpopular political or religious opinions, the English system protected those dissidents in their private beliefs, as well as the papers and other documents that might reveal those beliefs.

In American law, an even stronger protection for freedom of thought can be found in the First Amendment. Although the First Amendment text speaks of free speech, press, and assembly, the freedom of thought is unquestionably at the core of these guarantees, and courts and scholars have consistently recognized this fact. In fact, the freedom of thought and belief is the closest thing to an absolute right guaranteed by the Constitution. The Supreme Court first recognized it in the 1878 Mormon polygamy case of Reynolds v. United States, which ruled that although law could regulate religiously inspired actions such as polygamy, it was powerless to control “mere religious belief and opinions.” Freedom of thought in secular matters was identified by Justices Holmes and Brandeis as part of their dissenting tradition in free speech cases in the 1910s and 1920s. Holmes declared crisply in United States v. Schwimmer that “if there is any principle of the Constitution that more imperatively calls for attachment than any other it is the principle of free thought—not free thought for those who agree with us but freedom for the thought that we hate.” And in his dissent in the Fourth Amendment wiretapping case of Olmstead v. United States, Brandeis argued that the framers of the Constitution “sought to protect Americans in their beliefs, their thoughts, their emotions and their sensations.” Brandeis’s dissent in Olmstead adapted his theory of tort privacy into federal constitutional law around the principle of freedom of thought.

Freedom of thought became permanently enshrined in constitutional law during a series of mid-twentieth century cases that charted the contours of the modern First Amendment. In Palko v. Connecticut, Justice Cardozo characterized freedom of thought as “the matrix, the indispensable condition, of nearly every other form of freedom.” And in a series of cases involving Jehovah’s Witnesses, the Court developed a theory of the First Amendment under which the rights of free thought, speech, press, and exercise of religion were placed in a “preferred position.” Freedom of thought was central to this new theory of the First Amendment, exemplified by Justice Jackson’s opinion in West Virginia State Board of Education v. Barnette, which invalidated a state regulation requiring that public school children salute the flag each morning. Jackson declared that:

If there is any fixed star in our constitutional constellation, it is that no official, high or petty, can prescribe what shall be orthodox in politics, nationalism, religion, or other matters of opinion or force citizens to confess by word or act their faith therein. . . .

[The flag-salute statute] transcends constitutional limitations on [legislative] power and invades the sphere of intellect and spirit which it is the purpose of the First Amendment to our Constitution to reserve from all official control.

Modern cases continue to reflect this legacy. The Court has repeatedly declared that the constitutional guarantee of freedom of thought is at the foundation of what it means to have a free society. In particular, freedom of thought has been invoked as a principal justification for preventing punishment based upon possessing or reading dangerous media. Thus, the government cannot punish a person for merely possessing unpopular or dangerous books or images based upon their content. As Alexander Meiklejohn put it succinctly, the First Amendment protects, first and foremost, “the thinking process of the community.”

Freedom of thought thus remains, as it has for centuries, the foundation of the Anglo-American tradition of civil liberties. It is also the core of intellectual privacy.

“The New Home of Mind”

“Governments of the Industrial World, you weary giants of flesh and steel, I come from Cyberspace, the new home of Mind.” So began “A Declaration of Independence of Cyberspace,” a 1996 manifesto responding to the Communications Decency Act and other attempts by government to regulate the online world and stamp out indecency. The Declaration’s author was John Perry Barlow, a founder of the influential Electronic Frontier Foundation and a former lyricist for the Grateful Dead. Barlow argued that “[c]yberspace consists of transactions, relationships, and thought itself, arrayed like a standing wave in the web of our communications. Ours is a world that is both everywhere and nowhere, but it is not where bodies live.” This definition of the Internet as a realm of pure thought was quickly followed by an affirmation of the importance of the freedom of thought. Barlow insisted that in Cyberspace “anyone, anywhere may express his or her beliefs, no matter how singular, without fear of being coerced into silence or conformity.” The Declaration concluded on the same theme: “We will spread ourselves across the Planet so that no one can arrest our thoughts. We will create a civilization of the Mind in Cyberspace. May it be more humane and fair than the world your governments have made before.”

In his Declaration, Barlow joined a tradition of many (including many of the most important thinkers and creators of the digital world) who have expressed the idea that networked computing can be a place of “thought itself.” As early as 1960, the great computing visionary J. C. R. Licklider imagined that “in not too many years, human brains and computing machines will be coupled together very tightly, and that the resulting partnership will think as no human brain has ever thought.” Tim Berners-Lee, the architect of the World Wide Web, envisioned his creation as one that would bring “the workings of society closer to the workings of our minds.”

Barlow’s utopian demand that governments leave the electronic realm alone was only partially successful. The Communications Decency Act was, as we have seen, struck down by the Supreme Court, but today many laws regulate the Internet, such as the U.S. Digital Millenium Copyright Act6and the EU Data Retention Directive. The Internet has become more (and less) than Barlow’s utopian vision—a place of business as well as of thinking. But Barlow’s description of the Internet as a world of the mind remains resonant today.

It is undeniable that today millions of people use computers as aids to their thinking. In the digital age, computers are an essential and intertwined supplement to our thoughts and our memories. Discussing Licklider’s prophesy from half a century ago, legal scholar Tim Wu notes that virtually every computer “program we use is a type of thinking aid—whether the task is to remember things (an address book), to organize prose (a word processor), or to keep track of friends (social network software).” These technologies have become not just aids to thought but also part of the thinking process itself. In the past, we invented paper and books, and then sound and video recordings to preserve knowledge and make it easier for us as individuals and societies to remember information. Digital technologies have made remembering even easier, by providing cheap storage, inexpensive retrieval, and global reach. Consider the Kindle, a cheap electronic reader that can hold 1,100 books, or even cheaper external hard drives that can hold hundreds of hours of high-definition video in a box the size of a paperback novel.

Even the words we use to describe our digital products and experiences reflect our understanding that computers and cyberspace are devices and places of the mind. IBM has famously called its laptops “ThinkPads,” and many of us use “smartphones.” Other technologies have been named in ways that affirm their status as tools of the mind—notebooks, ultrabooks, tablets, and browsers. Apple Computer produces iPads and MacBooks and has long sold its products under the slogan, “Think Different.” Google historian John Battelle has famously termed Google’s search records to be a “database of intentions.” Google’s own slogan for its web browser Chrome is “browse the web as fast as you think,” revealing how web browsing itself is not just a form of reading, but a kind of thinking itself. My point here is not just that common usage or marketing slogans connect Internet use to thinking, but a more important one: Our use of these words reflects a reality. We are increasingly using digital technologies not just as aids to our memories but also as an essential part of the ways we think.

Search engines in particular bear a special connection to the processes of thought. How many of us have asked a factual question among friends, only for smartphones to appear as our friends race to see who can look up the answer the fastest? In private, we use search engines to learn about the world. If you have a moment, pull up your own search history on your phone, tablet, or computer, and recall your past queries. It usually makes for interesting reading—a history of your thoughts and wonderings.

But the ease with which we can pull up such a transcript reveals another fundamental feature of digital technologies—they are designed to create records of their use. Think again about the profile a search engine like Google has for you. A transcript of search queries and links followed is a close approximation to a transcript of the operation of your mind. In the logs of search engine companies are vast repositories of intellectual wonderings, questions asked, and mental whims followed. Similar logs exist for Internet service providers and other new technology companies. And the data contained in such logs is eagerly sought by government and private entities interested in monitoring intellectual activity, whether for behavioral advertising, crime and terrorism prevention, and possibly other, more sinister purposes.

Searching Is Thinking

With these two points in mind—the importance of freedom of thought and the idea of the Internet as a place where thought occurs—we can now return to the Google Search Subpoena with which this chapter opened. Judge Ware’s opinion revealed an intuitive understanding that the disclosure of search records was threatening to privacy, but was not clear about what kind of privacy was involved or why it matters.

Intellectual privacy, in particular the freedom of thought, supplies the answer to this problem. We use search engines to learn about and make sense of the world, to answer our questions, and as aids to our thinking. Searching, then, in a very real sense is a kind of thinking. And we have a long tradition of protecting the privacy and confidentiality of our thoughts from the scrutiny of others. It is precisely because of the importance of search records to human thought that the Justice Department wanted to access the records. But if our search records were more public, we wouldn’t merely be exposed to embarrassment like Thelma Arnold of Lilburn, Georgia. We would be less likely to search for unpopular or deviant or dangerous topics. Yet in a free society, we need to be able to think freely about any ideas, no matter how dangerous or unpopular. If we care about freedom of thought—and our political institutions are built on the assumption that we do—we should care about the privacy of electronic records that reveal our thoughts. Search records illustrate the point well, but this idea is not just limited to that one important technology. My argument about freedom of thought in the digital age is this: Any technology that we use in our thinking implicates our intellectual privacy, and if we want to preserve our ability to think fearlessly, free of monitoring, interference, or repercussion, we should embody these technologies with a meaningful measure of intellectual privacy.

Excerpted from “Intellectual Privacy: Rethinking Civil Liberties in the Digital Age” by Neil Richards. Published by Oxford University Press. Copyright 2015 by Neil Richards. Reprinted with permission of the publisher. All rights reserved.