Abstract
With the rise of science, 18th-century logic and rhetoric began to make use of inductive patterns of discourse. In logic, William Duncan discussed two methods of organizing extended discourse, the methods of analysis and synthesis. Analysis represents the movement of thought as the thinker or writer works through a problem to discover its solution. This method is actually an early form of what is now known as problem solving that Joseph Priestley, a rhetorician as well as a scientist, introduced into rhetoric. He uses analysis in his scientific writing, especially in his Experiments on Different Kinds of Air, in the form of a five-stage mental operation or heuristic that records the progress of his thoughts as he experimented on air to isolate and identify oxygen.