_Root Metaphor Theory_ is a theory of metaphysics.
Thirty years after World Hypotheses: A Study in Evidence (1942), Stephen C. Pepper reflected on the wider sense of Metaphor in Philosophy (1973) compared to Root Metaphors.
A Critical Appraisal of Root Metaphor Theory (1987) was written by [Ronald K. Hoeflin](https://en.wikipedia.org/wiki/Ronald_K._Hoeflin) as a theory of truth.
The Root of Metaphor Theory of Metaphysics (1935) published in the _Journal of Philosophy_ was a lead-in, 7 years before the release of World Hypotheses: A Study in Evidence (1942) by Stephen C. Pepper.