Sabine Winters is a freelance philosopher of science, with a strong focus on philosophy of space. Furthermore, Sabine is the founder and director of Future Based, an interdisciplinary philosophy platform through which she organizes meetups and publishes podcasts and articles. Currently, Sabine is doing research as a philosopher in residence on the role of imagination at ESA ESTEC Advanced Concept Team. Through research and further study, Sabine aims to specialize further in the philosophy of space science, with the goal of bringing more philosophy to the space industry.
A post by Sabine Winters
Somnium, seu Opus posthumum de astronomia lunari – ‘The Dream, or Posthumous Work on Lunar Astronomy’ by Johannes Kepler (1571–1630) tells the (story of a dream about the) adventures of Duracotus who, after much wandering and lengthy training in astronomy, is transported to the Moon by occult forces and the services of a demon. It was written over a period of more than 21 years (1609–1630) and published posthumously in 1634 by Kepler’s son Ludwig. Somnium discusses a wide range of topics but most extensively the movement of the Earth around its own axis, as Kepler writes:
The object of my Somnium, was to work out, through the example of the Moon, an argument for the motion of the Earth; or rather, to overcome objections taken from the general opposition of mankind. (Kepler, Somnium, ed. Lear (1965), Note 3,89.)
Somnium is not simply an exercise of idle imagination, full of metaphors and allegories for their own sake. Rather, Somnium aims to foster a better understanding of the structures of the universe by actively prompting the audience to imagine what (the motions of) the Earth would look like from the Moon. In this perspective, Somnium should be understood a thought experiment in which imagination is a guide to epistemic possibilities.
The fiction of Duracotus’ trip to the Moon was a means for Kepler to communicate scientific thinking but, even more importantly, the fictional narrative was intended to help the audience envision what could not be perceived directly. Somnium aims to persuade the reader to reach new insights and draw the right conclusion by testing assumptions and presenting arguments to support the essential truth of the Copernican theory. Through Somnium, (implicitly) Kepler asks his audience the question ‘What if we could travel to the Moon and look at the Earth from there, what would we see?’ By dint of a detailed, imaginary scenario in which people travel to the Moon and from there are able to see the Earth’s rotation around its own axis, Kepler provides his audience with a guide for a process of reasoning.
Not only is the work entertaining to read, but it also conveys the epistemological principles that challenged and changed the scientific worldview of his time. Through the heuristic use of fiction and imagination, Somnium invites the reader to join the story, where the reader is challenged to test their assumptions and background knowledge. In this sense, Somnium resembles a thought experiment and should be interpreted as a device for exploration, transporting the reader between enquiry and conclusion.
Science in the Fiction
Somnium, treated as a thought experiment, uses imagination to describe persons, events, situations and environments. The cohesion of all these elements described in the imagination scenario are connected by the fictional narrative. Thus, the definition of ‘fiction’ is an imaginary scenario in a narrative form. However, if Somnium is envisioned as merely offering a fictional possibility, the thought experiment is merely an exercise of the imagination and would do the work injustice. And indeed, there can be found a vast amount of literature where Somnium is considered as science fiction, and although the scientific relevance of advancing the Copernican theory is often underlined, the epistemological objective of the Somnium if often neglected. Somnium is a thought experiment precisely because Somnium employs the imagination as a device for scientific speculation. Considering Somnium as a literary work instead of a thought experiment undermines Kepler’s main objective (see introduction) of proving that the Earth rotates around its own axis.
The objective of Somnium is a clear indication that Kepler was not aiming solely for a literary exercise of the imagination; he wanted to impart (conceptual) knowledge through the contemplation of an imaginary scenario. The hypothesis of Somnium is not a fiction: The story of Somnium was not intended to explain astronomical mechanisms; rather, it aims to explain the relative aspects of movement and non-movement. Somnium, as a thought experiment, describes the (imaginary) scenario of standing on the Moon, where the experimenter is offered a (alternative) possibility for the actual world (seeing the Earth rotate around its axis). Somnium asks its readers (implicitly) how the Earth would look if seen from the Moon. Kepler’s aim was that through the execution of the experiment in the mind, the reader would gain new insights into the real world. Taking into consideration the epistemological purpose behind Somnium as a thought experiment, the question emerges of how a fictional story can lead to new insights about the actual world.
A Point of View
In Epitome Astronomiae Copernicanae Book 5, Chapters 5 and 6 (‘On the Annual Movement of the Earth’ and ‘On the Diurnal Revolution of the Terrestrial Body around its Axis and its Effect in Moving the Moon’, 1618–1621), one can find the exact same arguments for the rotation of the Earth around its own axis as in Somnium. The period of writing is overlapping: While working on the Epitome, Kepler was simultaneously working on Somnium. In Epitome a question-and-answer structure attempts to remove all uncertainties about the Copernican theory. Whereas in his Epitome Kepler presents arguments in a clear structure, in Somnium the fictional narrative leads. And here emerges an all-important difference between the Epitome and Somnium. In the Epitome everything is described from the perspective of the Earth, among Earthlings, and the Earth’s perspective is assumed throughout. The services of the demon and the fiction of the Somnium, by contrast, provide a quite different viewpoint – a (imaginary) view from the Moon.
Kepler faced the great challenge of demonstrating why the movement of the Earth was not observable, and thus that our senses are deceptive. Kepler skilfully and with the greatest care employed the entertaining nature of fiction, hiding within it his thought process of which few were yet convinced. In doing so, Somnium as a thought experiment engages the reader to employ their imagination as a device for exploring a new perspective in which, piece by piece, Kepler’s theory unfolds. In my master’s thesis drawing from Kristian Camilleri’s arguments I argue that going through a thought experiment brings about a way of reasoning that involves making judgments on assumptions and background knowledge and thus, a certain expertise is required to fully grasp the thought experiment. When going through Somnium, as a thought experiment the reader is encouraged to make judgments about their background knowledge and assumptions.
The key idea is that the imaginary scenario in Somnium not only reveals what is wrong with the original (Ptolemaic) theory, but also reveals at what points it is problematic. An argument is less powerful in this way. While one could argue that by contemplating an imaginary scenario, the premises and the conclusion of a thought experiment can be reconstructed into a logical argumentation form, I would counter that the process of imagining the Earth rotating around its own axis, cannot. Somnium is employing the imagination to perform an effort in being somewhere else, so as to provide non-logical knowledge. Thus, the ‘being somewhere else’ is a process of reasoning that cannot be put into arguments, because one would lose the ‘experience’, the visualisation of being on the Moon and watching the Earth. In doing so, Somnium enhances a process of reasoning through imagination in which (in successful cases) the reader gains new insights of the structures of the universe as proposed by Kepler.
Conclusion
When answering the question ‘What is learned in Somnium by imagining the Earth from the Moon?’, an argumentative, logical construction may emerge from the fitful narrative. However, there is an essential difference that reflects the contemplation of the imaginary scenario that appeals to a certain kind of reasoning: Somnium’s imaginary scenario offers the reader a peek into the universe in a way a logical argument cannot. The epistemological value of the imagination is that it provides a detached view from the Earth as well as from the scientific consensus of its time, in order to come to a new perspective, and helping us to ‘see’ the bigger picture. Focusing exclusively on the literary force of the work overlooks the characteristics of Somnium that enable it to offer a possible worldview to its readers.