This theory reveals the great uncertainty into which man’s thinking about the world of the senses had arrived at that time. Clinging to ideas inherited from antiquity, man’s consciousness was already so far restricted to the forming of pure matter-bound concepts that he was tempted to conceive heat as a material element. To this heat-substance the name ‘phlogiston’ was given. At the same time, under the Contra-Levitatem maxim, it was impossible to conceive of substance except as ponderable substance. This led to the conviction that whenever heat appears as a result of some treatment of matter (combustion or friction), the material substance subject to this treatment must lose weight.