The understanding of what knowledge consists in, how it is to be secured, the means by which discoveries are to be made, and the means by which purported knowledge is to be legitimated or confirmed were all questions that were disputed intensely in the course of the sixteenth and seventeenth centuries. These disputes were partly the outcome of developments in natural philosophy, but in some cases they lay partly at the source of these developments. They began, in the early sixteenth century, with reflection on Aristotle’s doctrine of method and scientific explanation, but soon turned into increasingly radical revisions to this doctrine. By the beginning of the seventeenth century, they took the form of a search for a wholly new approach, with several different, novel methodological models being advocated. The search for a satisfactory method is not a wholly linear development, however, and two sets of factors serve to overdetermine what is already quite a complex issue. The first turns on the fact that questions of method not only have direct connections to substantive developments in natural philosophy itself, but also to the relation between natural philosophy and the other disciplines (most notably metaphysics and theology), as well as to the question of what kinds of skills and virtues the practitioner of natural philosophy requires. Secondly, questions about the appropriate method for scientific disciplines become translated into questions about the legitimation of the scientific enterprise as a whole.

Philosophers in antiquity and in the early modern era reflected on and probed the nature of philosophical activity, asking what its legitimacy consisted in. But the kinds of answers that they came up with differed in a number of fundamental ways. The contrast for Plato and Aristotle was between the genuine philosopher and the sophist, whereas for early modern philosophers it was often between the secular natural philosopher and the scholastic. In both cases questions of intellectual honesty are paramount, but these are very much more in the foreground in the early modern period. Here they come to centre on the issue of commitment to a system, as charges of intellectual dishonesty are brought against those who argue from the standpoint of a purported systematic understanding. I explore this shift as part of a redefinition of the persona of the natural philosopher.

THE ORIGINS OF THE PHILOSOPHER

The question of what it means to be a philosopher goes back to the origins of the understanding of what philosophy is, which we can trace to Plato and the immediate Platonist tradition. This tradition was not a disinterested one. Its concern was not to discover what had been meant by ‘philosophy’ – the Presocratics had in fact designated what they were doing as historia (enquiry) – but to carve out and shape a particular kind of discourse for its own purposes, providing it with a genealogy and characterising it in a way that marginalises its competitors.

Individuals and the societies in which they live establish and maintain identity in relationship to some sense of a past, principally of interest insofar as it is of practical relevance in the present. The relationship may be unreliable: memories may be mischievous, a heritage fanciful, a history fabricated, or so brutally abridged as to be mythic. Regardless of the confidence with which a ‘past-relationship’ is assumed, however, its disruption can be deeply destabilising. These commonplaces about what Michael Oakeshott called the ‘practical past’ are no less pertinent to academic disciplines than they are to societies and individuals. The history of political theory, for example, still sometimes presented as an on-going tradition of debate and dialogue reaching back to the ancient Greeks, was invented as an authenticating lineage for the newly institutionalised university study of politics only around the end of the nineteenth century. Much the same might be said of the gatherings of canonic texts conventionally studied as histories of national literatures. In all these cases, the posited history retains its shape, momentum and character by the competing needs to affirm, reform or subvert a contemporary disciplinary activity. Such histories are often so present-centred as to be largely convenient lineages, anachronistic in predication of content and ‘whiggish’ in narrative structure.

In many ways the history of philosophy is at one with, and may have been a model for, the patterns of these adjacent academic genealogies.

In Part IV of the Principia, Descartes made the Earth an object of natural–philosophical/scientific investigation for the first time. There had, of course, been theories about such phenomena as earthquakes and volcanic activity, but these were considered – most notably by Aristotle – to be something that affected only the superficial layers of the Earth: the Earth's great mass was inert. As Jacques Roger has put it, Descartes' was ‘the first attempt to understand systematically the Earth's structure and its actual topography’. Having not only moved the Earth from the centre of the cosmos, but also made it little more than a piece of refuse from another solar system, Descartes puts himself in a position where he can consider it in the same way as any other concentration of solid matter, and indeed can consider any other planet as being like the Earth. Descartes is not unaware of the radical consequences of what he is advocating. As he points out to Burman:

THE PROJECT OF THE PRINCIPIA

Part I of the Principia covers much the same material that Descartes had already set out in the Meditationes, and Descartes tells one correspondent that ‘it is only an abridgement of what I wrote in the Meditationes’. The Meditationes, however, gives every impression of being self-contained, whereas Part I of the Principia is only one of six Parts of the project as initially envisaged, and effectively forms an introduction to what follows by providing a metaphysical basis for the natural philosophy that is developed there. In understanding the role of Part I in the larger project, it will be helpful to begin by mapping out the dangers, as we will have to steer a path through the Charybdis of treating the remainder of the Principia as an appendage to Part I, and the Scylla of treating Part I as a redundant introduction to the remainder.

If the Meditationes is as self-contained as it appears, we must ask what the purpose of the Principia is. Certainly, on one widespread reading of the Meditationes, the real novelty and originality of Descartes' project consist in his showing, by means of a project of radical doubt, the need for foundations for knowledge, and then providing these foundations, so that we might reconstruct anew the world that Meditation I called into doubt.

On 30 September 1640, Descartes wrote to Mersenne:

Mersenne presumably informed Descartes that the abridgement or abstract he was seeking was the Summa Philosophiæ of Eustachius a Sancto Paulo (first published 1629), for six weeks later he tells Mersenne that it seems to him ‘the best book of this kind ever written’. Nevertheless, his general opinion of the material it abstracts is low, and he tells Mersenne that he does not believe ‘the diversity of views among the Scholastics makes their philosophy difficult to refute, for it is easy to overturn the foundations, on which they all agree, and, this being done, all their disagreements will seem beside the point [inept]’.