The rise of classical field theory had its deep roots in the search for an efficient cause of apparent actions at a distance. In the case of electromagnetism, Thomson and Maxwell in their ether field theory succeeded in explaining the distant actions by introducing a new entity, the electromagnetic field, and a new ontology, the continuous ether. The field possessed energy and thus represented physical reality. But as a state of the mechanical ether, it had no independent existence. In Lorentz's electrodynamics, the field was still a state of the ether. However, since Lorentz's ether was deprived of all material properties and became synonymous with a void space, the field enjoyed an independent ontological status on a par with matter. Thus in physical investigations there emerged a new research programme, the field theory programme based on a field ontology, in contrast with the mechanical programme based on a particle ontology (together with space and force).

The new programme acquired a fresh appearance in Einstein's special theory of relativity (STR), in which the superfluous ontology of the Lorentz ether was removed from the theoretical structure. But in some sense the field theory programme was not yet completed. In Lorentz's electrodynamics as well as in STR, the fields had to be supported by a space (or spacetime). Thus the ultimate ontology of these field theories seemed not to be the fields, but the space (or spacetime), or more exactly the points of spacetime. As we shall see in chapter 4, this hidden assumption concerning the ultimate ontology of a field theory was not without consequences.