Ignatius L. Donnelly in the context of "Catastrophism"

Atlantis (Ancient Greek: Ἀτλαντὶς νῆσος, romanized: Atlantìs nêsos, lit. 'island of Atlas') is a fictional island mentioned in Plato's works Timaeus and Critias as part of an allegory on the hubris of nations. Purposely creating a literary contrast with the Achaemenid Empire, the great land-based power that ruled the east (what the Greeks called Asia), Plato describes Atlantis as a naval empire from the west that had conquered most of Europe and Libya, but then loses divine favor after an ill-fated campaign against a fictionalized Athens and subsequently submerges into the Atlantic Ocean. By portraying the victorious Athens in the image of his ideal state from the Republic, Plato intended the Atlantis story to bear witness to the superiority of his concept of a state.

Despite its minor importance in Plato's work, the Atlantis story has had a considerable impact on literature. The allegorical aspect of Atlantis was taken up in utopian works of several Renaissance writers, such as Francis Bacon's New Atlantis and Thomas More's Utopia. On the other hand, nineteenth-century amateur scholars misinterpreted Plato's narrative as historical tradition, most famously Ignatius L. Donnelly in his Atlantis: The Antediluvian World. Plato's vague indications of the time of the events (more than 9,000 years before his time) and the alleged location of Atlantis ("beyond the Pillars of Hercules") gave rise to much pseudoscientific speculation. As a consequence, Atlantis has become a byword for any and all supposed advanced prehistoric lost civilizations and continues to inspire contemporary fiction, from comic books to films.

Immanuel Velikovsky (/ˌvɛliˈkɒfski/; Russian: Иммануи́л Велико́вский, IPA: [ɪmənʊˈil vʲɪlʲɪˈkofskʲɪj]; 10 June [O.S. 29 May] 1895 – 17 November 1979) was a Russian-American psychoanalyst, writer, and catastrophist. He is the author of several books offering pseudohistorical interpretations of ancient history, including the U.S. bestseller Worlds in Collision published in 1950. Velikovsky's work is frequently cited as a canonical example of pseudoscience and has been used as an example of the demarcation problem.

His books use comparative mythology and ancient literary sources (including the Old Testament) to argue that Earth suffered catastrophic close contacts with other planets (principally Venus and Mars) in ancient history. In positioning Velikovsky among catastrophists including Hans Bellamy, Ignatius Donnelly, and Johann Gottlieb Radlof [de], the British astronomers Victor Clube and Bill Napier noted "... Velikovsky is not so much the first of the new catastrophists ...; he is the last in a line of traditional catastrophists going back to mediaeval times and probably earlier." Velikovsky argued that electromagnetic effects play an important role in celestial mechanics. He also proposed a revised chronology for ancient Egypt, Greece, Israel, and other cultures of the ancient Near East. The revised chronology aimed at explaining the so-called "dark age" of the eastern Mediterranean (c. 1100–750 BC) and reconciling biblical accounts with widely accepted archaeology and Egyptian chronology.