This lecture begins a series describing the development of organic chemistry in chronological order, beginning with the father of modern chemistry, Lavoisier. The focus is to understand the logic of the development of modern theory, technique and nomenclature so as to use them more effectively. Chemistry begins before Lavoisier’s "Chemical Revolution," with the practice of ancient technology and alchemy, and with discoveries like those of Scheele, the Swedish apothecary who discovered oxygen and prepared the first pure samples of organic acids. Lavoisier's Traité Élémentaire de Chimie launched modern chemistry with its focus on facts, ideas, and words. Lavoisier weighed gases and measured heat with a calorimeter, as well as clarifying language and chemical thinking. His key concepts were conservation of mass for the elements and oxidation, a process in which reaction with oxygen could make a "radical" or "base" into an acid.