Karl Popper's search for a philosophy of science which does not rely upon induction or presume psychologism resulted in his adoption of a pluralistic metaphysic that posits three separate worlds: W1, W2 and W3.¹ In part I we show that the notion of "world three" suffers from an important episte­mological inconsistency embedded in Popper's "principle of transference," according to which "...what is true in logic is true in psychology."² This inconsistency does not arise in Edmund Husserl's analysis of essential (de jure logical) structures, as contrasted to empirical (de facto, psychological) structures. Yet Husserl's analysis is motivated by his own critique of induction and psychologism.³ Therefore, after giving a brief sketch of Popper's solution and the inconsistency which it engenders, Part II presents Husserl's solution—which requires an epistemological, rather than ontological, pluralism.