FORMULATION OF THE CONCEPT

Few dicta are more inextricably linked with the Middle Ages than the declaration that “nature abhors a vacuum.” Although the full significance of this famous principle would be described and explicated only in the fourteenth century, it had already emerged in the thirteenth, when expressions such as natura abhorret vacuum, horror vacui, and fuga vacui began to appear. The origin of the principle is, however, unknown. But already in the first half of the twelfth century, Adelard of Bath expressed the fundamental idea of nature's resistance to a vacuum. In denying that magic plays any role in the failure of water to pour out of the holes in the bottom of a clepsydra when the holes in the top are stopped up, Adelard explained this strange phenomenon in cosmic terms by observing that