Although thinkers had been groping for two hundred years for the idea of a field - something that would transmit forces across the vastness of interstellar space - it was not until Faraday and Maxwell that field theory in the modern sense was born. Not really in the modern sense, of course, because it was not initially decided whether fields are merely mathematical descriptions of a deeper reality or are themselves physical entities that occupy the absolute space of Newton. Maxwell certainly regarded the electromagnetic field as something physical, but he was curiously unwilling to ascribe to it an independent existence as a ‘nonmechanical’ entity in its own right.

Even Einstein, in the early years of this century, was unwilling to ascribe an independent existence to the gravitational field. Instead he made the bold advance of expressing it, not as something that occupies space-time, but as a property, curvature, of space-time itself, and he tried to develop a geometrical theory of the electromagnetic field as well.

The question ‘Are fields merely mathematical descriptions of a deeper reality, or are they independent physical entities?’ and questions like it, recur over and over in different guises. As titillating as such questions may be to some philosophers, the modern response to them is surely that they are irrelevant.