Grammar and Logic at Port-Royal Grammar and logic make their appearance at Port-Royal within a system of relationship that were at once anthropological and technical; it is the latter which are examined here. Grammar is subjected to the principle of the reference of facts of language to thought. But this principle does not suffice in resolving all problems and sorne are thus referred to logic which, for its part, analyses the syllogism by basing itself on the theory of parenthetical clauses, and assimilates the results of grammar in order to transcend the level of simple syllogisms. The web of relationships thus woven between logic and grammar seems to encourage the joint development of the two disciplines; however, it in fact constitutes an obstacle to this development, for it imposes on each the constraint of respecting the limits of the other.