The problem of universals held that individuals point to supra-individual universals, essences, or forms—a position held by Plato's theory of the forms among many others. Instead, Ockham maintained that only individuals exist, and that universals are the products of abstraction from individuals by the human mind and have no extra-mental existence. Ockham himself asserted that names of an object do not point to an independent essential form, rather that they primarily exist as a mental concept, then as words, following the trend of conceptualism as well as nominalism, for whereas conceptualists held that they were mental concepts, i.e. the names were names of concepts, which do exist, although only in the mind, and nominalists held that universals were merely names, i.e. words rather than existing realities. He maintained that the existence of such universals would constrain God's creative process and would likewise limit the power of God and were an unnecessary plurality in our understanding of existence.
Ockham is also increasingly being recognized as an important contributor to the development of Western constitutional ideas, especially those of limited responsible government. The views on monarchial accountability espoused in his Dialogus (written between 1332 and 1348) greatly influenced the Conciliar movement and assisted in the emergence of democratic ideologies.
In logic, Ockham worked rigorously towards what would later be called De Morgan's Laws and considered ternary logic, that is, a logical system with three truth values—a concept that would be taken up again in the mathematical logic of the ninteenth and twentieth centuries.
Problems with Radical Realism
Following implications in John Scotus Erigena, also in Paul and Philo of Alexandria, there was a spiritual creation of pure kinds--one human, one dog, one cow. Initially, is attractive theologically: In one human (Adam), all "humans" (as mere images of Adam) fell, and in one human (Christ, the second Adam) all humanity is redeemed. No real individuals. Karl Barth: Jesus is the only true human being: Loss of individual realities led inevitably to pantheism (no real difference between humans and God), the implication that Creation was the Fall, and that Satan and Hell are mere privation, and ultimately rejection of creatio ex nihilo in favor of Erigena's emanation theory.
Abelard's criticism of realism (including moderate realism) can be explained in the diagram below. What we see here is the problem of Platonic participation and the absurdity of "fleeing" forms. We also note the impossibility of a human participating only in the rational part of animality.
"The varieties of. . . moderate realism turned on the answer to the question of whether, in an individual, the common nature is (1) really [i.e., ontologically] distinct from the individuating principle; or (2) "formally distinct," as Duns Scotus proposed; or (3) distinct only according to the mode of consideration, although involving some 'foundation in the thing' for such distinguishability, as Aquinas held.
"Ockham considered all forms of this doctrine of common natures in individual things to be self-contradictory and irrational. If the human nature of Socrates is really distinct from Socrates, then it is not Socrates' nature or essence, for a thing cannot be said to be essentially something that it really is not. If the common nature is anything at all, it is either one thing or many things; if one and not many, it is not common but singular, and if not one but many, then each of the many is singular and there is still nothing common."