The Fourth Amendment protects against unreasonable searches, but for decades a doctrine of surprising breadth has narrowed that protection: the so-called third-party doctrine. Under it, a person who voluntarily conveys information to another party - a bank, a telephone company, an internet provider - retains no reasonable expectation of privacy in that information, and the government may therefore obtain it without a warrant. The doctrine's original logic was intuitive enough. One who tells a secret to an acquaintance assumes the risk that the confidant will repeat it; likewise, the reasoning ran, one who hands financial records to a bank assumes the risk that the bank will surrender them to the state. Privacy, on this view, is forfeited by the act of disclosure itself. Whatever the merits of that logic when it was first articulated, its application to the digital environment strains credulity. The premise of voluntary disclosure presupposes a meaningful choice not to disclose. Yet participation in modern life is scarcely possible without generating a continuous stream of records held by third parties: every call routed, every website visited, every location registered by a phone as it pings nearby towers. To characterize the resulting data as voluntarily conveyed is to stretch the word beyond recognition, for the conveyance is an unavoidable byproduct of using the instruments of ordinary existence, not a considered decision to surrender information. A pedestrian does not assume the risk of comprehensive surveillance merely by carrying a telephone. Nor does the analogy to the repeated secret survive scrutiny. The confidant who betrays a secret discloses a single, discrete fact. The aggregation of digital records, by contrast, can reconstruct a person's movements, associations, and beliefs with a granularity no human informant could supply. A doctrine framed for isolated disclosures was never designed to govern the sustained, automated accumulation of an individual's entire digital life. Quantity, at some threshold, becomes a difference in kind. Some defenders of the doctrine respond that any recalibration should come from legislatures, not courts, since elected bodies are better positioned to weigh the competing interests of law enforcement and privacy. There is force in this institutional argument, and courts should not lightly displace legislative judgment. But the Fourth Amendment is not a statute to be amended at legislative convenience; it is a constitutional guarantee whose meaning courts are bound to interpret. When a doctrine premised on a factual assumption - that disclosure to a third party is voluntary in any ordinary sense - is overtaken by technological change that falsifies the assumption, a court does not usurp the legislature by declining to extend the doctrine to circumstances its rationale never contemplated. It merely declines to let an outdated fiction do constitutional work. None of this requires abolishing the third-party doctrine outright. A bank depositor who knowingly shares a specific record may still be said to assume a corresponding risk. The narrower claim is that the doctrine's mechanical extension to bulk digital data cannot be justified by the rationale that originally supported it - and that a guarantee against unreasonable searches, to remain meaningful, must track the realities of how information is now generated and held.