 No, I feel you are badly confused.  GRAVITY: the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface. then there is the theory of gravity which applies math to make predictions. And also there have been many 'evolutionary theories'. But evolution is a process not a theory. In psychology there is 'learning' and many 'theories of learning' And there is 'sound' and theories of sound. I can believe 'evolution' happens without accepting Darwin's explanations or LaMarc's or Lysenkos or Gould's etc. I can believe in 'Cancer' but there are many 'theories' of why Cancer happens and I can accept any of those theories or none of them.    