Handbook of the History of Logic: - Fordham University Faculty

668 Russell Wahl
century, the logic of ideas. Like other authors of the seventeenth century, Arnauld
and Nicole were very critical of the old logic, which for them included not only the
“scholastic” work on syllogisms, but also the humanistic logic of Ramus. They saw
their logic as new and they were particularly influenced by Descartes, who had
also been critical of syllogistic logic, and they incorporated many of his doctrines
into their work. This new seventeenth-century logic, with its rejection of much
traditional logic and its concern with clarifying ideas and determining the truth of
simple propositions, has often been criticized by more recent logicians of mixing
psychology and epistemology with logic. Often it has been compared unfavorably
with mediaeval logic. 3 Despite the fact that most of its topics are closer to the
mediaeval period, the Port-Royal Logic has a very modern feel to it, and covers
several topics now included in more informal introductory logic courses, such as
discussions of clarification of concepts, informal fallacies, causal reasoning, and
probability, as well as more traditional accounts of propositions and syllogisms.
2 THE NATURE OF LOGIC
Descartes had not written a specific treatise on logic but had developed his method
in the unpublished Rules for the Direction of the Mind and his later Discourse
on Method. A manuscript of the Rules had been made available to Arnauld and
Nicole, and they even incorporated a portion of this work in their own. 4 Descartes’
focus was on clarifying simple ideas and developing a method which would lead to
new truths. His view was that the mind had no trouble making inferences, 5 but
that it did have trouble discerning what was before it clearly and distinctly. His
method was developed to help the mind solve problems and more clearly discern
truths. Descartes recognized two operations of the intellect which help it reach
this goal, intuition and deduction. Intuition, he said, was not “the fluctuating
testimony of the sense or the deceptive judgement of the imagination . . . but the
conception of a clear and attentive mind, which is so easy and distinct that there
can be no room for doubt about what we are understanding” [Adam and Tannery,
1964-76, X, 368; Cottingham et al., 1985-1991, I, 14]. He was less clear on what he
3 [Kneale and Kneale, 1962, 315–320], is relatively more sympathetic toward the Port-Royal
logicians, but [Bochesnski, 1961, 258], does not mince words when summing up classical seventeenth
century logic: “Poor in content, devoid of all deep problems, permeated with a whole
lot of non-logical philosophical ideas, psychologist in the worst sense.” Norman Kretzmann’s
long article on the History of Semantics [Kretzmann, 1967, 378–379], is also quite critical of the
Port-Royal Logic. [Ashworth, 1974] has some opening remarks which are also quite critical of
logic during this period.
4 Adam and Tannery state that Clerselier gave Arnauld and Nicole the manuscript of the
Rules after the first edition of the Logic appeared in 1662. The portion from Rule 13 included in
Part IV, Chapter 2, was included in the second (1664) edition of the Logic [Adam and Tannery,
1964-76, X, 352].
5 Descartes is notorious for stating that “while our experiences of things are often deceptive,
the deduction or pure inference of one thing to another can never be performed wrongly by an
intellect which is in the least degree rational” [Cottingham et al., 1985-1991, I, 12; Adam and
Tannery, 1964-76, X, 365]. This was an opinion shared by Arnauld and Nicole.