Francis Bacon and the practices of measurement.

The instrumental character of Francis Bacon's natural and experimental histories was often noted, but never fully investigated. In this paper I aim to reconstruct the theoretical and methodological background which supports this feature. I claim that we can read large parts of the second book of Bacon's as a guide to laboratory practices; and that it was read in this manner by some of Bacon's seventeenth century followers. Key to this guide is Bacon's theory of prerogative instances which, in turn, provides the grounding for a whole theory of instruments of detection and instruments of measurement. I show, in particular, how Bacon suggested that such instruments can be used for 'charting' virtues and powers; a process in which instruments of detection can be transformed into instruments of measurement. I also show that Bacon's views on instruments entail an elaborated conception of measurement which departs from the ethos of artisanal perfection. Instead of pursuing the 'best results', Bacon's instrumental natural and experimental histories aim to offer a large enough corpus of correlations, estimates and calculations which, taken together, can represent more or less accurately changes and variations of natural virtues and powers.