Guillaume Danet, Les Art des armes (1766):
Because it assures one’s defense, the parry should be considered as the most essential part of fencing, and yet we see it as the most neglected today. If it is useful to know how to thrust with precision and speed, it is still more advantageous to know how to deflect your adversary’s thrusts because as soon as one has acquired the surety of the parry, it quickly becomes routine and soon offers more opportunities to riposte safely.
Nicolas Demeuse, Nouveau traité de l’art des armes (1778)
The parry of demi-circle is one of the most advantageous, because, by parrying the demi-circle, you lead your sword to the inside of the engagement and inside the arms, and, by that, you uncover your adversary’s body in front of your point.
La Boëssière, Traité de l’Art des armes (1818)
One important thing on which we particularly insist is that the parries should be done without force. It is this lightness—or rather this precision—of movements that alone provides the means to touch the opponent. Tension and hardness in the parries are so disadvantageous that, a skilled fencer with a light hand, realizing these faults in his adversary, continually seeks to make him succumb to them. He deliberately forces the adversary to parry, and, at the least attempted levering of his point, quickly removes it. Here we have one of the finesses and one of the great mischiefs of the art.
Columbia Classical Fencing, LLC 