Abstract
I begin by briefly recalling two facts of seventeenth century intellectual history: not only is a fourth part devoted to method added to the three parts traditionally contained in logic treatises, but in a number of texts the terms "logic" and "method" are blurred. I then give an explanation of these two facts with the following ideas: 1/ Since the criticism of Aristotelian sciences at the beginning of the seventeenth century was in particular focused on logic, the question was asked as to what could replace or supplement it. 2/ Although method was very generally supposed to fulfil this function, its objectives were not clear. I propose a distinction between four ideas of method, which I call method-disposition, method-demonstration, method-invention and method-purification. 3/ The blurring between logic and method comes partly from the fact that some of these ideas take up elements of the then existant logic, but, in a context marked by the reception of Descartes's work, we must also take into account the fact that, since Descartes had not composed a logic and since he had not really explain what his method was, his successors were looking for what both might have been.