There existed essentially two theories of light during the early nineteenth century: the particulate theory and the wave theory. This we realise today is a gross over-simplification, since there were many varieties of each theory. But to the supporters of one theory the other theory had faults so fundamental that no distinction between varieties of the same theory was sufficient to placate opposition to that theory. This meant that opponents of either the wave or the particulate theory seldom, in their attacks, distinguished between different varieties of either theory.
