The case of Edward Snowden raises many questions. Do we need the surveillance programs he disclosed to mitigate the threat of terrorism? Do those programs intrude excessively on individual privacy? If we need them, and the intrusions on privacy are not too great, was it appropriate to keep them secret? Is their effectiveness compromised by public disclosure? Could they have been disclosed in another way? If not, was Edward Snowden justified in disclosing them unilaterally?

The answers to the first two questions depend on each other. If the surveillance programs of the National Security Agency provide real protection against terrorism, many of us would put up with a substantial intrusion on our privacy. On the other hand, if those programs are not shown to protect us, our tolerance for government snooping would decline commensurately.

We regularly give up some portion of our privacy—as when we submit to screening before boarding a plane—if the intrusion seems minimal and the benefit, in the form of safety, seems substantial. When the invasion of privacy is greater, we have heightened concerns. Many of us think that maintaining limits on the power of the state to gather and store information on our thoughts, our bodies, our relationships, and certain other aspects of our lives, is important. We want strict controls on such practices.

In thinking about these questions, Americans should be aware of the sorry history of political surveillance in the United States. Surveillance by the federal government began in 1908 with the establishment of the Bureau of Investigation in the Department of Justice (later the Federal Bureau of Investigation, or FBI). During World War I, the Bureau gathered information on those opposing American entry into the war or opposing the draft, leading to many hundreds of prosecutions under the 1917 Espionage Act and the 1918 Sedition Act. Large numbers were sent to prison for five, 10, or even 20 years for peaceful dissent.

Following the war, the Bureau stepped up its surveillance, focusing on labor activists, aliens, and suspected communists and anarchists, leading to dragnet arrests of thousands and the summary deportations of hundreds. In 1924, the Justice Department imposed some limits on the FBI, but most restrictions were ended about the time World War II started in Europe in 1939. From then until shortly after the death of long-time FBI Director J. Edgar Hoover in 1972, political surveillance dominated the work of the FBI. Its activities included extensive programs to harass and disrupt the lives and organizations of leftists, civil rights advocates, anti-war activists, and many others. Political surveillance peaked during the Nixon Administration. Disclosures by whistleblowers of that era and the Watergate scandal helped lead to a number of Congressional investigations.

So far as we now know based on Snowden’s revelations, the NSA has neither engaged in the politically targeted practices of an earlier era nor in the harassment of political dissenters. That makes its activity a great deal less objectionable than what took place previously. On the other hand, in collecting metadata on virtually every phone call in the United States in recent years, the NSA has compiled information that could reveal a great deal about us. As US Supreme Court Justice Sonia Sotomayor pointed out in an opinion in a 2012 case not involving terrorism, it can reveal calls “to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar, and so on.” As there is no way to guarantee that we will never again have officials like J. Edgar Hoover or Richard Nixon, the availability of such information on all of us is not a comforting thought for those concerned about privacy.

Aryeh Neier is the president emeritus of the Open Society Foundations.