From Influence to Inhabitation: The Transformation of Astrobiology in the Early Modern Period

This dissertation presents a conjoined and comparative history of astrology and the debate about the existence of extraterrestrial (ET) life in the early modern period. These two histories are usually kept separate, largely because the same period represents a certain terminus ad quem for the former and the terminus a quo for latter. The sixteenth and seventeenth centuries saw the decline or marginalisation of astrology—the dismantling of the celestial causal chain of Aristotelian cosmology and the dismissal of any planetary or astral influence outside of light, heat and gravitation. They also saw the adoption, or re-adoption, of the cosmological view concerning the existence of a plurality of worlds in the universe (pluralism) and the possibility of ET life. Both these trends are considered as consequences of a Copernican cosmology and hallmarks of a modern worldview. The modern and in some sense artificial delineation between these two strands of historical enquiry (i.e. the history of astrology and the history of pluralism) may be detrimental, both to our understanding of celestial philosophy at any given time, as well as to our appreciation of cosmological change over longer periods. The most general and obvious similarity is that both these concepts meld astronomy and the life sciences. Astrology is concerned with the effect of the celestial realm on terrestrial biology (celestial influence), while pluralism is predicated on the possible existence of biological processes in the heavens (celestial inhabitation). In the mid 1990s, a new discipline was founded which similarly unites astronomy and biology under a common goal. This discipline is astrobiology, an interdisciplinary science which combines the search for ET life with the study of terrestrial biology—especially its origins, evolution, and occurrence in extreme environments—in an attempt to understand the very nature of life itself within a larger cosmological context. This thesis proposes that a history of astrobiology may provide the perfect vehicle to connect the more established histories of astrology and the ET life debate. The results of research undertaken so far suggest two main hypotheses. The first argument is that, in its infancy, Renaissance and early modern pluralism was in fact encouraged by evolving theories of celestial influence. The second is that, as the seventeenth century progressed, certain thinkers began to consciously oppose the concepts of influence and inhabitation as rival teleological models for astronomical cosmology. The demonstration of these arguments will contribute to the history of both astrology and pluralism. The marginalisation of astrology can be better understood by appreciating the appeal of pluralism and how it came to be placed in juxtaposition to astrology. At the same time, the history of our modern obsession with life elsewhere in the universe can be enriched by examining how the new paradigm, to use Kuhnian phrasing, grew out of the old.