The term “idea” in the seventeenth century is notoriously difficult. Not only does each major thinker have their own understanding of “idea”—many of those thinkers themselves move ambiguously between different meanings. This confusion is generally attributed to Descartes. While ideas had only existed in the mind of God, Descartes consciously made new use of the term by applying it to things in human minds. At the same time, Descartes left many questions about what an idea is. Given Descartes’ own ambiguity, (...) the various doctrines of ideas developed by Arnauld, Malebranche, Locke, Spinoza and Leibniz, all have some legitimate claim as interpretations of Descartes. (shrink)

According to the received view (Bocheński, Kneale), from the end of the fourteenth to the second half of nineteenth century, logic enters a period of decadence. If one looks at this period, the richness of the topics and the complexity of the discussions that characterized medieval logic seem to belong to a completely different world: a simplified theory of the syllogism is the only surviving relic of a glorious past. Even though this negative appraisal is grounded on good reasons, it (...) overlooks, however, a remarkable innovation that imposes itself at the beginning of the sixteenth century: the attempt to connect the two previously separated disciplines of logic and mathematics. This happens along two opposite directions: the one aiming to base mathematical proofs on traditional (Aristotelian) logic; the other attempting to reduce logic to a mathematical (algebraical) calculus. This second trend was reinforced by the claim, mainly propagated by Hobbes, that the activity of thinking was the same as that of performing an arithmetical calculus. Thus, in the period of what Bocheński characterizes as ‘classical logic’, one may find the seeds of a process which was completed by Boole and Frege and opened the door to the contemporary, mathematical form of logic. (shrink)

The aim of the paper is to illuminate some core aspects of Leibniz’s conception of judgement and its place in his conception of the mind. In particular, the paper argues for three claims: First, the act of judgement is at the centre of Leibniz’s conception of the mind in that minds strive at actualising innate knowledge concerning derivative truths, where the actualising involves an act of judgement. Second, Leibniz does not hold a judgement account of predication, but a two-component account (...) that distinguishes between predication and alethic evaluation. Third, Leibniz understands the act of affirmative judgement in terms of establishing active dispositions, i.e. strivings, to make reasons available for future reasoning that aims at answering whether-questions. Correspondingly, he understands the act of negative judgement in terms of establishing dispositions to ban propositions from future reasoning that aims at answering whether-questions. In the final analysis, the acts of affirmative as well as of negative judgement turn out to be acts of changing memory dispositions. (shrink)

Gottfried Wilhelm Leibniz (1646–1716) was one of the great thinkers of the seventeenth and eighteenth centuries and is known as the last “universal genius”. He made deep and important contributions to the fields of metaphysics, epistemology, logic, philosophy of religion, as well as mathematics, physics, geology, jurisprudence, and history. Even the eighteenth century French atheist and materialist Denis Diderot, whose views could not have stood in greater opposition to those of Leibniz, could not help being awed by his achievement, writing (...) in his Encyclopedia, “Perhaps never has a man read as much, studied as much, meditated more, and written more than Leibniz… What he has composed on the world, God, nature, and the soul is of the most sublime eloquence. If his ideas had been expressed with the flair of Plato, the philosopher of Leipzig would cede nothing to the philosopher of Athens.” (Vol. 9, p. 379) Indeed, Diderot's mood was almost despairing in a remark from another piece, which also has a great deal of truth in it: “When one compares the talents one has with those of a Leibniz, one is tempted to throw away one's books and go die quietly in the dark of some forgotten corner.” More than a century later, Gottlob Frege, who fortunately did not cast his books away in despair, expressed similar admiration, declaring that “in his writings, Leibniz threw out such a profusion of seeds of ideas that in this respect he is virtually in a class of his own.” (“Boole's logical Calculus and the Concept script” in Posthumous Writings , p. 9) The aim of this entry is primarily to introduce Leibniz's life and summarize and explicate his views in the realms of metaphysics, epistemology, philosophical theology, and natural philosophy. (shrink)