The Hague: Adriaan Moetjens, 1698. First edition, an exceptional copy, ruled in red throughout and in a richly decorated contemporary binding, of Huygens’s posthumously published final work, in which he expounds his theories about the possibility of life on other planets, linking them to Copernican thought: “A man that is of Copernicus’s opinion, that this Earth of ours is a planet, carried round and enlightened by the Sun, like the rest of them, cannot but sometimes have a fancy, that it’s not improbable that the rest of the planets have their dress and furniture, nay and their inhabitants too as well as this Earth of ours” (pp. 1-2 of the English translation, 1698). “Presented as a letter to his brother Constantijn and written in Latin, the Kosmotheoros consists of two books, containing a discussion of the possibility of life on other planets, an overview of the Copernican system, a critique of Cartesian vortex cosmology, and several new (and revolutionary) calculations concerning the measurements of the planets and the solar system … Not only do the conjectures on the plurality of worlds make use of his older work on probability and astronomy, the Kosmotheoros is Huygens’ only work that offers a comprehensive philosophical framework to his mechanical worldview, and consequently his scientific achievements” (van der Schoot). “
First edition, an exceptional copy, ruled in red throughout and in a richly decorated contemporary binding, of Huygens’s posthumously published final work, in which he expounds his theories about the possibility of life on other planets, linking them to Copernican thought: “A man that is of Copernicus’s opinion, that this Earth of ours is a planet, carried round and enlightened by the Sun, like the rest of them, cannot but sometimes have a fancy, that it’s not improbable that the rest of the planets have their dress and furniture, nay and their inhabitants too as well as this Earth of ours” (pp. 1-2 of the English translation, 1698). “Presented as a letter to his brother Constantijn and written in Latin, the Kosmotheoros consists of two books, containing a discussion of the possibility of life on other planets, an overview of the Copernican system, a critique of Cartesian vortex cosmology, and several new (and revolutionary) calculations concerning the measurements of the planets and the solar system … Not only do the conjectures on the plurality of worlds make use of his older work on probability and astronomy, the Kosmotheoros is Huygens’ only work that offers a comprehensive philosophical framework to his mechanical worldview, and consequently his scientific achievements” (van der Schoot). “In the second part of Cosmotheoros, Huygens discussed the different movements of the heavenly bodies and how they must appear to the inhabitants of the planets. He took the occasion to mention new advances in astronomy. He compared the intensity of light from various heavenly bodies – thus making the first attempt at photometry. In contrast to most other Huygensian writings, Cosmotheoros has had wide appeal and a broad readership, and has been translated into several languages” (DSB). This first edition is surprisingly scarce in commerce: ABPC/RBH list only seven other copies in the past 50 years.
The question of whether other celestial bodies could be inhabited, or the ‘plurality of worlds’, was already discussed by the pre-Socratic philosophers, from Thales to Democritus. Plutarch, in his treatise De facie in orbe Lunae (1st century AD), established that the Moon is a second Earth and discussed whether it is habitable. But the discoveries made possible by the telescope, early in the seventeenth century, spurred a new fascination with what has been called “the modern scientific moon voyage.” Johannes Kepler, the father of modern astronomy, left at his death a vision of serpentine moon creatures, Somnium (1634), and John Wilkins, one of the founders of the Royal Society, wrote an influential fantasy, The Discovery of a New World; or, A Discourse tending to prove, that it is probable there may be another Habitable World in the Moon (1638). The most systematic early account of extraterrestrial life, however, was Christiaan Huygens’s Cosmotheoros. Huygens opens his work with a criticism of those of Kepler and Wilkins, and of Athanasius Kircher’s Ecstatic Journey (1660), which excluded the possibility of extraterrestrial life.
“The first book of the Kosmotheoros offers an extensive argumentation in support of the existence of a plurality of worlds in the planets. Through a series of ‘probable conjectures’, Huygens presents his thoughts on how these planetary inhabitants might look, how they might live, and what they might believe and know. According to Huygens, Copernican astronomy demonstrates the astronomical similarity between the Earth and the other planets in the solar system. Moreover, the development of the telescope has made it possible to observe the physical resemblance of Earth to the celestial bodies, which appear to have hills, mountains, seas, and clouds. Huygens therefore argues that it is possible to theorize about life on the planets in analogy to the world we see around us. He legitimizes this by drawing on his epistemological ideas about the vital role of probability and the absence of absolute certainty in the study of nature in general, concluding that ‘enough material is available for probable conjectures’. This argument reflects an important departure from the rationalistic and mechanistic philosophy of Descartes, which Huygens had supported in his early work, i.e. that the study of nature deals not with absolute certainties, but with degrees of probability: ‘in such noble and sublime studies as these, it is a glory to arrive at probability, and the search itself rewards the pain’.
“Despite the importance of astronomical evidence and a method based on probability and analogy, the argument for planetary life is ultimately based on a different type of reasoning. Huygens uses a teleological argument to defend that the planets are not just created for the sake of mankind, but must all have their own inhabitants: “Since then the greatest part of God’s creation, that innumerable multitude of stars, is placed out of the reach of any man’s eye; […] is it such an unreasonable opinion, that there are some reasonable creatures who see and admire those glorious bodies at a nearer distance?”
“With the formulation of this analogical method, Huygens has laid out the program for the first book. The argument is repeated time and again as Huygens discusses many different aspects of planetary life: since our planet is found to be solid, we can assume that the planets are solid; since our planet has an atmosphere, we can assume that the planets have an atmosphere as well; since life exists on earth, we can assume that life exists on the other planets; since our planet hosts intelligent life, we can assume that other planets do so as well; since humankind builds houses, we can assume that planetary intelligent inhabitants build houses too; and since we know geometry, we can assume that the planetary inhabitants do so too” (van der Schoot).
“In the second of the two books making up his treatise, he scrutinizes astronomical observations related to life elsewhere. An analysis of his arguments reveals, however, that whereas his evidences against life on the moon are detailed and nearly decisive, the empirical support he finds for life on the planets is slim. For example, he infers that spots seen on Jupiter are clouds and, as such, evidences of water, although he departs from his stress on uniformity by suggesting that different forms of water may exist on the various planets. His empirically based attribution of a thick “Atmosphere surrounding Venus” is one of the anticipations of modern results credited to Huygens, but he leaves unanswered the problem of how his Venusian astronomers would overcome this obstacle to observation. He recognizes the excessive heat brought by the sun to the inner planets and the deficiency in heat for the more remote planets, but he says little in explanation of how their inhabitants adjust to these conditions. In short, much of his commendable presentation of observation is contrary or irrelevant to planetary life. He fares better in discussing life beyond our solar system. One cannot but praise his attempt to estimate the distance of the stars from an analysis of how far our sun would have to be removed to make it comparable in brightness to Sirius; this he capably uses to urge that our failure to detect planets around stars is to be expected. Huygens falls somewhat into overstatement in his claim that “all the greatest Philosophers of our Age … have the Sun of the same nature as the fix’d Stars,” and he uses a weak form of argument in asking “why may not every one of these Stars or Suns have as great a retinue as our Sun, of Planets, with their Moons …?” Nonetheless, the first of these ideas was gaining ever-increasing acceptance, and the second was not far behind.
“In assessing the scientific character of Huygens’s Cosmotheoros, a crucial consideration is how he presented his conclusions. In this regard, he deserves high praise; conjectures abound, but conjectures they are labelled and their relative probabilities assessed. This feature of his book goes far to justify it as a scientific treatise, especially in the context of the hypothetico-deductive methodology of science championed by Huygens in the preface to his classic Treatise on Light.
“One of the least known but most important influences of Huygens’s Cosmotheoros involved England’s Royal Astronomer, John Flamsteed, who recommended the Cosmotheoros to the vicar of Greenwich, Archdeacon Thomas Plume (1630-1704). Plume’s fascination with it led him to bequeath 1,902 pounds to Cambridge University to “erect an observatory and to maintain a professor of astronomy and experimental philosophy, and to buy or build a house with or near the same.” Thus came to be established the Plumian professorship of astronomy at Cambridge, a position held by some of the most distinguished astronomers of modern times” (Crowe, pp. 21-22).
“Huygens did not believe that complete certainty could be achieved in the study of nature, but thought that the philosopher must pursue the highest degree of probability of his theories. Clearly Huygens considered this degree to be adequate in the case of his explanations of light and gravity. It is difficult for the historian to assert how plausible, in comparison with those explanations, Huygens considered his theories about life on other planets and about the existence of beings comparable to man … The argument of the book is very methodically set forth, and its earnestness suggests that Huygens did indeed assign a very high degree of probability to these conjectures. Huygens’ reasoning is that it is in the creation of life and living beings that the wisdom and providence of God are most manifest. In the Copernican world system—which is sufficiently proved as agreeing with reality—the earth holds no privileged position among the other planets. It would therefore be unreasonable to suppose that life should be restricted to the earth alone. There must be life on the other planets and living beings endowed with reason who can contemplate the richness of the creation, since in their absence this creation would be senseless and the earth, again, would have an unreasonably privileged position” (DSB).
Although Huygens first planned to write this work in French, he later decided to publish it in Latin instead. He finished the manuscript in January 1695 and wrote to Constantijn that he had also found a publisher. On 4 March he wrote to Constantijn that the first page had already been printed but that the printer had not progressed any further. However, Christiaan’s health was rapidly deteriorating and on 8 July he passed away. In his last will, drawn up on 23 March, he requested Constantijn to see to it that his book was published. Unfortunately, Constantijn's duties as secretary to the stadholder-king William III often necessitated his presence in London and the printing of the book progressed slowly. Constantijn too passed away (on 12 November 1697) before it was finished and the last stages of the printing were overseen by the Leiden professor of mathematics and physics Burchard de Volder. “Within a few years after the publication of the Latin edition by bookseller Adriaan Moetjens in The Hague in 1698, under the full title Koσμoθɛωρoς, sive De Terris Coelestibus, earumque ornatu, conjecturae, the book was translated into English, Dutch, French and German. The Kosmotheoros remained popular and was reprinted many times throughout the eighteenth century. In 1717 even a Russian translation was published, personally commissioned by Peter the Great, although the publication was not uncontroversial and the Kosmotheoros was apparently considered a ‘Satanic perfidy’ by its unwilling Russian publisher” (van der Schoot).
“One of the earliest attempts to determine the intensity of light was from Huygens, who in the 17th century had tried to compare the brightness of the sun and that of the star Sirius. Huygens used a long tube with an adjustable aperture at the far end of the instrument. To make the comparison, he first pointed the tube to the sun and observed a diminished sunlight by reducing the size of the aperture. He then waited until the evening and pointed the tube to the star. Through adjusting the size of the aperture, he obtained a starlight with the same brightness as that of the sunlight. The intensity ratio of the sun and that of the star was in inverse proportion to the area ratio of the two openings (Huygens, 1698)” (Buchwald & Franklin, p. 163).
DSB VI, 611; Thorndike VII, 634 ff.; Roller-Goodman I, 575; Honeyman 1731; Bierens de Haan 2226; Winter, Compendium Utopiarum I, p. 67. Jed Z. Buchwald, A. Franklin (eds.), Wrong for the Right Reasons, 2006; Michael J. Crowe, The Extraterrestrial Life Debate 1750-1900: The Idea of a Plurality of Worlds from Kant to Lowell, 1986; Joas van der Schoot, ‘Interpreting the Kosmotheoros (1698). A historiographical essay on theology and philosophy in the work of Christiaan Huygens,’ De Zeventiende Eeuw. Cultuur in de Nederlanden in interdisciplinair perspectief 30 (2014), pp. 20–39.
4to (200 x 156mm), pp. [ii], 144, with six engraved plates (numbered 1-5, plate 4 in two states, five folding). Printer's device on title page, printer’s headpiece, engraved initials, ruled in red throughout. Contemporary calf, covers ruled in gilt, spine richly gilt with black morocco lettering-piece, all edges gilt (capitals neatly restored).