could be built up exclusively from some more or less complicated expression containing
, together with tensors derived from it; tensors of any other kind being barred. Physically speaking, this would indicate that atomic matter or bound energy, and in particular those forms of matter called electrons and protons, could be built up in terms of electromagnetic or loose energy. Even were we to succeed in this attempt we should not have banished all duality; for though we should have got rid of
, there would still remain a duality between
and the metrical field or
’s of space-time.
At any rate, all attempts to reduce matter to electromagnetic fields have thus far presented insuperable difficulties owing to the impossibility of accounting for those ultimate aspects of matter, the electron and proton, in terms of