Swordplay is described as both the science and the art of defence. One possible definition of a science is that one gains knowledge through precise, systematic study, based on observation and experience. A definition of an art is that one solves problems by applying the principles of the art, not by looking to a fixed set of solutions. A bout can be seen as a series of physical and mental problems to be solved.
In a simplistic way, the science part of swordplay covers the minutiae of making each technique work. Questions such as: How do I get mechanical advantage over my opponent’s blade? What line should the blade follow? How far should I step? etc. can be answered by systematic study and through personal experience, and the answers determine how each technique should be performed.
In a similarly simplistic manner, the art side of swordplay gives the swordsman a “tactical overview” that allows them choose the right technique(s) for the situation they are currently facing. And given that the no two encounters are ever exactly the same, it would be impossible to list every possible solution to the problems you may face.
The first chapters of the rapier treatises we study contain the core of these principles – tempo (timing), measure (distance), footwork etc. The techniques in the treatises should (I believe) be seen as a set of exemplars of the principles of the art and possibly as best-
Marozzo, our main sidesword treatise, is written in a slightly different order, teaching the techniques first through the set plays and then drawing out some of the core principles. However, the key is still to look for the rules that allow you to apply the techniques taught to any situation.
Ultimately, you should be able to apply the rules of the art so that, whatever situation you may find yourself in, you can fight with any weapons you may have cause to use.