The birth of chemistry as a science, in the modern sense, is closely connected with a revolutionary change in the conception of what can be called the chemical arch-process-combustion, or, to use a more scientific term, oxidation. This change arose out of the Contra-Levitatem maxim and the new conception of heat which this maxim required. In the old doctrine of the four Elements, Heat had been conceived as a manifestation of the element of Fire, and so, together with Air, as belonging to the realm of the 'uncreated things'. Hence the release of heat from created substance was always felt to be a sacred act, as is shown by the fire rites of old.