A plurality of inhabited worlds: life on other planets from the Renaissance to the Enlightenment

Galileo with his telescope in the Piazza San Marco, Venice. Wood engraving (Wellcome Collection).

During the Early Modern period, the learned community widely believed in the existence of anthropomorphic extra-terrestrials (Brake, 2006). Nevertheless, scholars disagreed on pretty much every other aspect of the topic, from the form that such extra-terrestrial societies might take, to their natural laws, languages, fauna and flora, theological status, forms of worship and governments. This blogpost explores this little-known dimension of Early Modern culture, and its evolution from the Renaissance to the Enlightenment.

The wider question of how the Western world transitioned within a century from a view where the existence of extra-terrestrial life was the norm to a contemporary one where life on Earth is possibly an exception has been the focus of renewed historical discussion in the last thirty years. This transition has been attributed to the joint advancement of astronomical knowledge and Western secularisation, which meant that traditional arguments about the plurality of inhabited worlds started to lose ground at the end of the Enlightenment period. This is not to say however that such ideas disappeared completely: contemporary historians such as Gabriel McKee have shown the enduring, influential presence of religion within contemporary science fiction (McKee, 2007). More broadly, beyond the field of history, the natural sciences have seen the apparition of exciting disciplines such as exobiology, while the growing interdisciplinary field of space humanities allows intellectual history, history of science, theology and literature to provide longue durée insights into those debates.

William Derham, Astro-theology, or a demonstration of the being and attributes of God from a survey of the heavens (London, 1715) (Heritage Auctions).

From the late Renaissance to the Enlightenment period, the debate about life on other planets was commonly known as the plurality of worlds. A sub-discipline of theology even emerged to deal specifically with the religious implications of the debate: the English bishop William Derham called it ‘Astro-theology’. The Early Modern taste for the plurality of worlds stemmed from the period’s renewed engagement with classical literature on the subject. Harking back to the Roman satirist Lucian of Samosata, travelogues to the moon had been common since Antiquity. According to Mark Brake, extra-terrestrial life was widely believed amongst the early Greek philosophers, particularly Epicureans. In Early Modern times ‘Every important cosmology of the seventeenth century and later holds Copernicanism, and pluralism, as a fundamental notion’ (Brake, 2006). This consensus was based on four main arguments.

The four main points of consensus within the plurality of worlds debate were concerned with arguments of teleology, plenitude, probability, and anthropomorphism. The argument of teleology was derived from Aristotelian scholasticism and postulated that the function of a world is to shelter life. Since the universe is filled with worlds, therefore these worlds must be filled with life.

The second argument of plenitude derived from the first: if the function of a world was indeed to shelter life, then God would most likely populate all the planets of the universe with life, as a universe filled with lifeless worlds would have no function.

The third argument of probability is the most familiar to us today: although Early Modern scholars clashed vividly about whether the universe was finite, indefinite (René Descartes) or infinite (Giordano Bruno, Henry More), most agreed that the universe contained so many worlds that the idea of life being present on only one planet verged on the absurd.

The argument of anthropomorphism finally discussed the forms that extra-terrestrial life would take. Strikingly, no one in the Early Modern period seemed to believe that extra-terrestrials could have a non-human form – although disagreements about size, height, skin colour, savagery and gait were common. This was largely because of the dominant Christian framework which held that God had made man in his image (Genesis 1:27), a consideration generally present in other Abrahamic religions, such as Islam and Judaism (Goushey, 2022).

Let us not be naive however: although natural philosophers might have agreed on basic arguments of teleology, plenitude, probability and anthropomorphism to support the likelihood of extra-terrestrial life, they still disagreed on pretty much everything else. Philip Almond summed it well by underlining that it was a debate in which, on its religious side, ‘only the most theologically brave ventured to go’ (Almond, 2006). On one hand, scholars like Johannes Kepler, Christian Huygens, Isaac Newton and Emanuel Swedenborg did see life on other planets as more than compatible with Christianity: for them it was yet another proof of the existence of God. Yet the theological issues it raised for Christianity were numerous: Giordano Bruno got burned for various reasons, including the wider arguments he inferred from his belief in the plurality of worlds. Major disagreements amongst the learned included whether anthropomorphic extra-terrestrials belonged to the Adamic race or to another variety of human (polygenesis); had there been a primordial couple on every planet? Had God incarnated himself under human form on other worlds as well? Or was there only one Messiah for the whole universe? If so, how could the Gentiles from outer space ever be saved? Would they ever go to heaven, or hell? If so, would it even be the same heaven as Earthlings?

Engraving by Bernard Picart for the Entretiens sur la pluralité des mondes (1686) in Œuvres diverses de Monsieur de Fontenelle, 3 vol. (La Haye, Gosse et Neaulme, 1728-1729), vol.1, between pages 148 and 149 (Bibliothèque nationale de France).

Because of these tensions, David Dunér has argued that a large consensus on extra-terrestrial life only fully emerged in the eighteenth century, as the question of life on other planets became claimed by physico-theologists, while in earlier periods it was a more divisive theological issue, as exemplified by the case of Giordano Bruno (Dunér, 2016). However, the possibility of an earlier widely held belief from the late Renaissance onwards might still be regarded as a possibility. Why? Because the plurality of worlds debate extended beyond astronomical and theological debates into a popular literary, satirical and philosophical genre derived from the classical tradition of Lucian of Samosata. This included works such as Kepler’s Somnium (1608), Francis Godwin’s The Man in the Moon (1638), Athanasius Kircher’s Itinerarium ecstaticum (1656), Cyrano de Bergerac’s Histoire comique des États et Empires de la Lune (1657), Margaret Cavendish’s The Blazing World (1666) and Bernard Le Bovier de Fontenelle’s Entretiens sur la pluralité des mondes (1686). These works show that popular belief in extra-terrestrial life found a widespread readership beyond specialist scientific or theological circles during the seventeenth century. In the eighteenth century, the topic became commonly discussed in the salons as a pleasant thought-experiment linked to travel literature, natural law or soul-body debates — Voltaire’s Micromégas (1752) discussed the two debates in the same story.

Finally, many travelogues to the moon and other planets, from Ludvig Holberg’s Nicolaii Klimi (1741) to Swedenborg’s De telluribus in mundo nostro solari (1758) exhibited common features with descriptions of indigenous people present in travel literature. This highlights the wider similarities between discussions of life on distant planets and life in distant lands, where the plurality of worlds served as an extension of Early Modern travelogues to reflect critically upon Western society.

Vincent Roy-Di Piazza

Readers interested in learning more about the history of the plurality of worlds can read Vincent Roy-Di Piazza’s open access article in the Annals of Science (2020).

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