Plato (through the character Critias in his dialogues) describes Atlantis as an island larger than Libya and Asia Minor put together, located in the Atlantic just beyond the Pillars of Hercules—generally assumed to mean the Strait of Gibraltar. Its culture was advanced and it had a constitution suspiciously similar to the one outlined in Plato’s “Republic.” It was protected by the god Poseidon, who made his son Atlas king and namesake of the island and the ocean that surrounded it. As the Atlanteans grew powerful, their ethics declined. Their armies eventually conquered Africa as far as Egypt and Europe as far as Tyrrhenia (Etruscan Italy) before being driven back by an Athenian-led alliance. Later, by way of divine punishment, the island was beset by earthquakes and floods, and sank into a muddy sea.
In 1679 the Swedish scientist Olaus Rudbeck published "Atland," a four-volume work in which he attempted to prove that Sweden was the original site of Atlantis and that all human languages were descended from Swedish. Though considered authoritative in his homeland, few outside of Sweden found Rudbeck’s arguments convincing.
Plato’s Critias says he heard the story of Atlantis from his grandfather, who had heard it from the Athenian statesman Solon (300 years before Plato’s time), who had learned it from an Egyptian priest, who said it had happened 9,000 years before that. Whether or not Plato believed his own story, his intent in telling it seems to have been to boost his ideas of an ideal society, using stories of ancient victory and calamity to call to mind more recent events such as the Trojan War or Athens’ disastrous invasion of Sicily in 413 B.C. The historicity of Plato’s tale was controversial in ancient times—his follower Crantor is said to have believed it, while Strabo (writing a few centuries later) records Aristotle’s joke about Plato’s ability to conjure nations out of thin air and then destroy them.
In the first centuries of the Christian era, Aristotle was taken at his word and Atlantis was little discussed. In 1627, the English philosopher and scientist Francis Bacon published a utopian novel titled “The New Atlantis,” depicting, like Plato before him, a politically and scientifically advanced society on a previously unknown oceanic island. In 1882, former U.S. Congressman Ignatious L. Donnelly published “Atlantis: The Antediluvian World,” which touched off a frenzy of works attempting to locate and learn from a historical Atlantis. Donnelly hypothesized an advanced civilization whose immigrants had populated much of ancient Europe, Africa and the Americas, and whose heroes had inspired Greek, Hindu and Scandinavian mythology. Donnelley’s theories were popularized and elaborated by turn-of-the-20th-century theosophists and are often incorporated into contemporary New Age beliefs.
From time to time, archaeologists and historians locate evidence—a swampy, prehistoric city in coastal Spain; a suspicious undersea rock formation in the Bahamas—that might be a source of the Atlantis story. Of these, the site with the widest acceptance is the Greek island of Santorini (ancient Thera), a half-submerged caldera created by the massive second-millennium-B.C. volcanic eruption whose tsunami may have hastened the collapse of the Minoan civilization on Crete.