In recent years a certain emphasis has been put by some scholars on Leibniz’s concern about empirical sciences and the relations between such concern and the development of his mature metaphysical system. In this paper I focus on Leibniz’s interest for the microscope and the astonishing discoveries that such instrument made possible in the field of the life sciences during the last part of the Seventeenth century. The observation of physical bodies carried out by the “magnifying glasses” revealed a matter (...) swarming everywhere with life and activity, contrary to the cartesian and atomistic view of matter as something sterile and passive. Moreover, the discovery of uncountable complete “animalcula” living in the smallest drop of water provided evidence for the idea of the preformation of every organism. During his lifetime, Leibniz was extremely watchful about the new microscopical discoveries and came into contact with some of the major “observers” of his time, such as Hooke, Leeuwenhoek, Swammerdam and Malpighi. Relying both on some passages in Leibniz’s texts and on recent critical studies, I will argue that important aspects of his metaphysics have been strongly affected by the empirical observation of the “invisible world” which the microscope made possible. In the last part of the paper I show how the concept of “preformation”, originally drawn from the context of the life sciences, comes to play in Leibnizʼs philosophy a very general role, going far beyond the scope of biology and shaping important aspects of his overall philosophical system. (shrink)

This paper presents a comprehensive study of Robert Boyle’s writings on seminal principles or seeds. It examines the role of seeds in Boyle’s account of creation, the generation of plants and animals, spontaneous generation, the generation of minerals and disease. By an examination of all of Boyle’s major extant discussions of seeds it is argued that there were discernible changes in Boyle’s views over time. As the years progressed Boyle became more sceptical about the role of seminal principles in the (...) generation of minerals and he came to reject the spontaneous generation of insects and animals from putrefying matter. It is also argued that Boyle’s notion of a generative or ‘plastick’ principle creates a tension within his mechanical philosophy. He appeals to a plastick power in order to explain those phenomena of generation that are beyond the explanatory resources of the corpuscular hypothesis. However, when pressed to explain the nature of this power he either hints, somewhat paradoxically, that it too can be explained mechanically or admits his nescience. (shrink)

In the late 1720s, Daniel Turner and James Blondel engaged in a pamphlet dispute over the power of the maternal imagination. Turner accepted the long-standing belief that a pregnant woman's imagination could be transferred to her unborn child, imprinting the foetus with various marks and deformities. Blondel sought to refute this view on rational and anatomical grounds. Two issues repeatedly received these authors' attention: the identity of imagination, and its power in pregnant women; and the process of generation and foetal (...) development. In their discussions of these issues, differences between the authors' acceptance of general medical theories and philosophies became apparent. Blondel invoked Newtonian matter theory, experimental philosophy, and iatro-mechanism, while Turner adhered more to the authority of the Ancients and advocated a more direct role for the Creator as an alternative to mechanism in explaining natural phenomena. Additionally, the authors held differing views of what they regarded as experience. The widespread contemporary interest in their dispute suggests that Turner and Blondel raised the phenomenon of the maternal imagination from an issue of folk belief to a concern of eighteenth-century medicine. (shrink)