Harold N. Lee has contended that metaphysical doctrines, such as solipsism and mind-matter dualism, should be interpreted as hypotheses.1 This claim is of considerable importance, for if it is correct, we should reject not only the traditional dogma that some metaphysical doctrines are “absolutely certain,” but also the skeptical rejoinder which the dogma frequently has evoked, namely that they cannot be knowledge at all. Lee’s proposal is a mean between these two extremes, since it permits metaphysical doctrines to be probable knowledge. It has the advantages of each extreme, and the defects of neither.