The variety of atomism especially associated with Boyle, and expounded in his Sceptical Chemist (1661) and The Origin and Form of Qualities (1666). Boyle held that all material substances are composed of minute corpuscles, themselves possessing shape, size, and motion. The different properties of materials would arise from different combinations and collisions of corpuscles: chemical properties, such as solubility, would be explicable by the mechanical interactions of corpuscles, just as the capacity of a key to turn a lock is explained by their respective shapes. In Boyle's hands the idea is opposed to the Aristotelian theory of elements and principles, which he regarded as untestable and sterile. His approach is a precursor of modern chemical atomism, and had immense influence on Locke. However, Locke recognized the need for a different kind of force guaranteeing the cohesion of atoms, and both this and the interactions between such atoms were criticized by Leibniz. See also action at a distance, field.