The third of four Maxims of Root Metaphors in World Hypotheses: A Study in Evidence (1942) builds on Maxim II: Each world hypothesis is autonomous.
While a new world hypothesis might be developed to be adequate, combining pre-existing world hypotheses would only serve to increase doubt on associated root metaphors. * Root metaphors are not to be mixed, and so world hypotheses shouldn't be mixed. This only leads to confusion. * The possibility of developing a new world hypothesis is left open ... but leaves an issue as to whether it could be declared adequate.
A broader understanding of this maxim can be aided by [a commentary by Bill J. Harrell (2004), paragraph 19](https://web.archive.org/web/20041110053845/http://people.sunyit.edu:80/~harrell/Pepper/bjh_pep01.htm) [editorial paragraphing added]:
> Pepper adds new depth and breadth to the rhetorician’s canon that one shall not mix metaphors. > While Pepper warns against eclecticism, he does not recommend that in practice we use only one world theory. > * Since each system has peculiar strengths and weaknesses, we may find in one context a world theory is more serviceable than another while the latter was more effectively applied in a different situation. > * We are likely to need all of the world hypotheses if we are to adequate ly deal with the substantive problems which confront our lives and our disciplines. > As the various world hypotheses emerged in all of their clarity there was the obvious motivation to choose the best or that failing, borrow the strengths of each to incorporate in an overarching and superior system. > * Unfortunately, this has led more to confusion than to greater theoretical adequacy. > * In fact, the root metaphor method suggests that if a better world hypotheses is ever created it will not be due to some final refinement of the existing world theories or some act of syntheses while maintaining the integrity of the different metaphors, but will be grounded in a new root metaphor. > * Pepper’s work in the final twenty-five years of his life was devoted mainly to refining a root metaphor into a world hypothesis of his own devising, selectivism. Clearly, he felt it dealt more adequately with problems inherent to the other four world systems but still did not claim he had established the greater adequacy of selectivism.
So, Pepper himself was developing a fifth world hypothesis, published as Concept and Quality (1966). Pepper did not, however, declare _selectivism_ as an Adequate World Hypothesis.
**eclecticism**, (from Greek _eklektikos_, “selective”), in philosophy and theology -- says the [Encyclopaedia Britannica](https://www.britannica.com/topic/eclecticism), is -- the practice of selecting doctrines from different systems of thought without adopting the whole parent system for each doctrine. It is distinct from syncretism -- the attempt to reconcile or combine systems -- inasmuch as it leaves the contradictions between them unresolved.
As opposed to a strengthening a pure world hypothesis, an attempt to create an eclectic fusion only weakens structural corroboration.
> §6. _Maxim III: Eclecticism is confusing_.
> This maxim follows from the second. If world hypotheses are autonomous, they are mutually exclusive. A mixture of them, therefore, can only be confusing. We are speaking now as having cognition in mind, not practice, which often entails other than purely cognitive considerations. > When we say that world theories are mutually exclusive, we do not mean that they stand apart from one another like so many isolated posts. Each theory is well aware of the others, criticizes and interprets them and entirely includes them within its scope. It is only from the perspective of common sense, in the recollection of the different theories' diverse courses of critical refinement, that we are aware of their mutual exclusiveness. [p. 104] > More perspicuously, it is only through our study of their factual conflicts, their diverse categories, their consequent differences of factual corroboration, and -- in a word -- their distinct root metaphors that we become aware of their mutual exclusiveness. [pp. 104-105]
Pepper strongly criticizes [Alfred North Whitehead](https://iep.utm.edu/whitehed/) Process & Becoming as eclectic.
> Yet it is a tempting notion, that perhaps a world theory more adequate than any of the world theories mentioned above (those bound to their metaphors) might be developed through the selection of _what is best_ in each of them and organizing the results with a synthetic set of categories. This seems to be the deliberate principle of method used by Whitehead in his _Process and Reality_. It is the eclectic method. Our contention is that this method is mistaken in principle in that it adds no factual content and confuses the structures of fact which are clearly spread out in the pure root-metaphor theories; in two words, that it is almost inevitably sterile and confusing. [p. 106]
Synthesizing multiple root metaphor theories result in categories that refuse to merge, and danda that refuse to haramonize. Selecting "the best" from multiple root metaphors will reduce adequacy.