The invisible object, in the eighteenth century, is not an evidence. It is the result of textual and semantic learning. Which concrete strategies are used to construct and depict objects out of sight? How do we make them a cognitive reality acceptable to a scientific community? This paper first highlights the conditions for the emergence of a field of microscopic knowledge and its epistemological consequences. Then we consider the microscopic gaze in terms of learning, situated between the act of observation (...) as such and discursive practices. We conclude by studying a concrete case of “negotiation of the invisible” in a correspondence between Carl Linnaeus and John Ellis concerning corpuscles observed in mushroom infusions. (shrink)

The History of scepticism from Erasmus to Spinoza is often called upon to support three theses: first, that Descartes had a dogmatic notion of systematic knowledge, and therefore of physics; second, that the hypothetical epistemology of physics which spread during the xviith century was the result of a general sceptical crisis; third, that this epistemology was more successful in England than in France. I reject these three theses: I point first to the tension in Descartes’ works between the ideal of (...) a completely certain science and a physics replete with hypotheses; further, I argue that the use of hypotheses by mechanical philosophers cannot be separated from their conception of physics; finally I show that, at the end of the xviith century, physicists in France as well as in England spoke through hypotheses and I examine different ways of explaining this shared practice. Richard H. Popkin’s book serves therefore as a starting point for insights into the general problem: to what extent and for what reasons some propositions in physics have been presented as hypotheses in the xviith century? (shrink)

This paper examines the status of medical experiments using the Leibnizian conception of knowledge. The aim is to consider whether experimentation is a “perceptive foretaste” or a real condition for the advancement of knowledge. To this end I argue, first, that acting on bodies could be a way to understand them and, second, I establish a place for medical experiments in the field of learning. In these ways, I identify a “provisional empiricism” in Leibniz’ medical texts.

The ArgumentMicroscopical consideration played a crucial role in German physiology in the period of, grosso modo, 1780–1830. Specifically, a conception of material change was established, according to which all life is grounded in the process of the generation of microscopical forms out of an amorphous, primitive generative substance. Embryological development, tissue growth, and the generation of microorganisms were all considered to be the manifestation of this fundamental developmental process. In contrast to the common historiography, I try to understand Theodor Schwann's (...) 1838 discovery of the cell theory in terms of the epistemological categories he applied to the prevailing conceptions of life and living matter. I argue that Schwann was able to discern cells not because of any superior microscopical methods, but rather as part of his wider investigative endeavor to explicate life processes according to specific causal agents. I argue that Schwann was able to demonstrate the existence of cells only when he considered animal tissues in terms of a causal relation between specific material agents and their effect, that is, the developmental history of tissue. (shrink)