The law under which the government collected this data, Section 215 of the Patriot Act, allows the F.B.I. to obtain court orders demanding that a person or company produce “tangible things,” upon showing reasonable grounds that the things sought are “relevant” to an authorized foreign intelligence investigation. The F.B.I. does not need to demonstrate probable cause that a crime has been committed, or any connection to terrorism.

Even in the fearful time when the Patriot Act was enacted, in October 2001, lawmakers never contemplated that Section 215 would be used for phone metadata, or for mass surveillance of any sort. Representative F. James Sensenbrenner Jr., a Wisconsin Republican and one of the architects of the Patriot Act, and a man not known as a civil libertarian, has said that “Congress intended to allow the intelligence communities to access targeted information for specific investigations.” The N.S.A.’s demand for information about every American’s phone calls isn’t “targeted” at all — it’s a dragnet. “How can every call that every American makes or receives be relevant to a specific investigation?” Mr. Sensenbrenner has asked. The answer is simple: It’s not.

The government claims that under Section 215 it may seize all of our phone call information now because it might conceivably be relevant to an investigation at some later date, even if there is no particular reason to believe that any but a tiny fraction of the data collected might possibly be suspicious. That is a shockingly flimsy argument — any data might be “relevant” to an investigation eventually, if by “eventually” you mean “sometime before the end of time.” If all data is “relevant,” it makes a mockery of the already shaky concept of relevance.

Let’s turn to Prism: the streamlined, electronic seizure of communications from Internet companies. In combination with what we have already learned about the N.S.A.’s access to telecommunications and Internet infrastructure, Prism is further proof that the agency is collecting vast amounts of e-mails and other messages — including communications to, from and between Americans.

The government justifies Prism under the FISA Amendments Act of 2008. Section 1881a of the act gave the president broad authority to conduct warrantless electronic surveillance. If the attorney general and the director of national intelligence certify that the purpose of the monitoring is to collect foreign intelligence information about any non­American individual or entity not known to be in the United States, the Foreign Intelligence Surveillance Court can require companies to provide access to Americans’ international communications. The court does not approve the target or the facilities to be monitored, nor does it assess whether the government is doing enough to minimize the intrusion, correct for collection mistakes and protect privacy. Once the court issues a surveillance order, the government can issue top-secret directives to Internet companies like Google and Facebook to turn over calls, e-mails, video and voice chats, photos, voice­over IP calls (like Skype) and social networking information.