William of Ockham
Frustra fit per plura, quod fieri potest per pauciora.
It is vain to do with more what can be done with less.
Essentia non sunt multiplicanda praeter necessitatem.
Entities should not be multiplied unnecessarily.
. . . the contradictory opposite of a copulative proposition is a disjunctive proposition composed of the contradictory opposites of its parts.
. . . the contradictory opposite of a disjunctive proposition is a copulative proposition composed of the contradictories of the parts of the disjunctive proposition.
Summa totius logicae (transl. P Boehner 1955)
[Note: This is Ockham's formulation of De Morgan's Laws.]