A cold wind is blowing across the landscape of privacy. The twin imperatives of technological advancement and coun­terterrorism have led to dramatic and possibly irreversible changes in what people can expect to remain of private life. Nearly 10 years ago Scott McNealy of Sun Microsystems famously pronounced the death of privacy. “Get over it,” he said. Some people, primarily those younger than about 25, claim to have done just that, embracing its antithesis, total public disclosure. And of course in many cases—determining the whereabouts of a terrorist or the carrier of a disease—public interest has an overwhelming claim on information that is usually private.

Yet in many contexts—banking, commerce, diplomacy, medicine—private com­­munications are essential. The founding fa­­thers of the Republic put great stock in personal privacy; privacy is embodied (though, as we are often reminded, not stated) in the Bill of Rights. In her keynote essay Esther Dyson clarifies what “privacy” means by reminding us what it is not: several important issues commonly labeled dilemmas of privacy are better understood as issues of security, health policy, insurance or self-pre­sentation.

Terrorism and digital connectedness have both made privacy a hot-button issue, but there are plenty of other good reasons to look closely at the future of privacy. One is the upcoming U.S. election, which is being held at a time of tremendous upheaval in the legal and legislative framework of government wiretapping.

A second is the allure of substantial benefits from disclosing certain kinds of information: en­hanced medical care through electronic medical and genetic records, for instance, or better protection from identity theft via biometric authorization. A third is that the threats posed by technology to personal privacy and even personal security are unprecedented, both from the unintended effects of increased self-disclosure as well as from the rapidly evolving sophistication of surveillance gadgetry, radio-frequency ID chips and data fusion—not to mention the viruses and other pests that infest the Internet.

In spite of all the threats to privacy, an astonishing variety of technology for protecting privacy has been devised, yet it lies virtually untapped. Maybe part of the reason is that so many young adults find all the anxieties about privacy to be much ado: many in the new generation are only too happy to trade their parents’ version of “private information” for a rich life in the fishbowl of social networking.

For all those reasons and more, the editors of Scientific American present this issue devoted to the future of what Supreme Court Justice Louis D. Brandeis called “the right to be let alone.”