Discovery doctrine  The discovery doctrine or doctrine of discovery is a concept of public international law expounded by the United States Supreme Court in a series of decisions, most notably "Johnson v. M'Intosh" in 1823. Chief Justice John Marshall explained and applied the way that colonial powers laid claim to lands belonging to foreign sovereign nations during the Age of Discovery. Under it, title to lands lay with the government whose subjects travelled to and occupied a territory whose inhabitants were not subjects of a European Christian monarch. The doctrine has been primarily used to support decisions invalidating or ignoring aboriginal possession of land in favor of colonial or post-colonial governments. The 1823 case was the result of collusive lawsuits where land speculators worked together to make claims to achieve a desired result. John Marshall explained the Court's reasoning. The decision has been the subject of a number of law review articles and has come under increased scrutiny by modern legal theorists. The Doctrine of Discovery was promulgated by European monarchies in order to legitimize the colonization of lands outside of Europe. Between the mid-fifteenth century and the mid-twentieth century, this idea allowed European entities to seize lands inhabited by indigenous peoples under the guise of discovery. In 1494, the Treaty of Tordesillas declared that only non-Christian lands could be colonized under the Doctrine of Discovery. In 1792, U.S. Secretary of State Thomas Jefferson declared that the Doctrine of Discovery would extend from Europe to the infant U.S. government. The Doctrine and its legacy continue to influence American imperialism and treatment of indigenous peoples. The plaintiff Johnson had inherited land, originally purchased from the Piankeshaw tribes. Defendant McIntosh claimed the same land, having purchased it under a grant from the United States. It appears that in 1775 members of the Piankeshaw tribe sold certain land in the Indiana Territory to Lord Dunmore, royal governor of Virginia and others. In 1805 the Piankeshaw conveyed much of the same land to William Henry Harrison, governor of the Indiana Territory, thus giving rise to conflicting claims of title. In reviewing whether the courts of the United States should recognize land titles obtained from Native Americans prior to American independence, the court decided that they should not. Chief Justice John Marshall had large real estate holdings that would have been affected if the case were decided in favor of Johnson. Rather than recuse himself from the case, however, the Chief Justice wrote the decision for a unanimous Supreme Court. Marshall found that ownership of land comes into existence by virtue of discovery of that land, a rule that had been observed by all European countries with settlements in the New World.