What else, besides magnetism or electricity, causes fields of attraction and repulsion?
The fundamental forces are electromagnetism, the weak and strong nuclear forces, and gravity. Of them, only gravity appears to be solely an attraction. The weak nuclear force is involved in radioactive decay, and can transfer momentum between electrons and neutrinos. It is now treated with electromagnetism as part of the electroweak force. The strong nuclear force is responsible for binding quarks together to form hadrons (including protons and neutrons), and the residual effects also bind these neutrons and protons together in the nucleus of the atom. Of course there are other potential fields of attraction and repulsion which are manifestations of the fundamental four, for example, the intermolecular force is an aspect of electromagnetism.
