In
scholasticism, William of Ockham advocated reform in both method and content, the aim of which was simplification. Ockham incorporated much of the work of some previous theologians, especially
Duns Scotus. From Duns Scotus, Ockham derived his view of divine omnipotence, his view of grace and justification, much of his epistemology and ethical convictions. However, he also reacted to and against Scotus in the areas of predestination, penance, his understanding of universals, his formal distinction (that is, "as applied to created things"), and his view of parsimony which became known as
Occam's razor.
Faith and reason William of Ockham espoused
fideism, stating that "only faith gives us access to theological truths. The ways of God are not open to reason, for God has freely chosen to create a world and establish a way of salvation within it apart from any necessary laws that human logic or rationality can uncover." He believed that science was a matter of discovery and saw God as the only ontological necessity.
Nominalism William of Ockham was a pioneer of
nominalism, and some consider him the father of modern
epistemology, because of his strongly argued position that only individuals exist, rather than supra-individual
universals, essences, or forms, and that universals are the products of abstraction from individuals by the human mind and have no extra-mental existence. He denied the real existence of metaphysical universals and advocated the reduction of
ontology. Ockham is sometimes considered an advocate of
conceptualism rather than nominalism, for whereas nominalists held that universals were merely names, i.e. words rather than extant realities, conceptualists held that they were mental
concepts, i.e. the names were names of concepts, which do exist, although only in the mind. Therefore, the universal concept has for its object, not a reality existing in the world outside us, but an internal representation which is a product of the understanding itself and which "supposes" in the mind the things to which the mind attributes it; that is, it holds, for the time being, the place of the things which it represents. It is the term of the reflective act of the mind. Hence the universal is not a mere word, as
Roscelin taught, nor a
sermo, as
Peter Abelard held, namely the word as used in the sentence, but the mental substitute for real things, and the term of the reflective process. For this reason Ockham has sometimes also been called a "
Terminist", to distinguish him from a nominalist or a conceptualist.
Efficient reasoning One important contribution that he made to modern science and modern intellectual culture was efficient reasoning with the principle of parsimony in explanation and theory building that came to be known as
Occam's razor. This maxim, as interpreted by
Bertrand Russell, states that if one can explain a phenomenon without assuming this or that hypothetical entity, there is no ground for assuming it, i.e. that one should always opt for an explanation in terms of the fewest possible causes, factors, or variables. He turned this into a concern for ontological parsimony; the principle says that one should not multiply entities beyond necessity——although this well-known formulation of the principle is not to be found in any of Ockham's extant writings. He formulates it as: "For nothing ought to be posited without a reason given, unless it is self-evident (literally, known through itself) or known by experience or proved by the authority of Sacred Scripture." For William of Ockham, the only truly necessary entity is God; everything else is contingent. He thus does not accept the
principle of sufficient reason, rejects the distinction between essence and existence, and opposes the
Thomistic doctrine of active and passive intellect. His scepticism to which his ontological parsimony request leads appears in his doctrine that human reason can prove neither the immortality of the soul; nor the existence, unity, and infinity of God. These truths, he teaches, are known to us by revelation alone. According to the principle of ontological parsimony, he holds that we do not need to allow entities in all ten of Aristotle's categories; we thus do not need the category of quantity, as the mathematical entities are not "real". Mathematics must be applied to other categories, such as the categories of substance or qualities, thus anticipating modern scientific renaissance while violating Aristotelian prohibition of
metabasis.
Theory of knowledge In the theory of knowledge, Ockham rejected the scholastic theory of species, as unnecessary and not supported by experience, in favour of a theory of abstraction. This was an important development in late medieval
epistemology. He also distinguished between intuitive and abstract cognition; intuitive cognition depends on the existence or non-existence of the object, whereas abstractive cognition "abstracts" the object from the existence predicate. Interpreters are, as yet, undecided about the roles of these two types of cognitive activities.
Political theory William of Ockham is also increasingly being recognized as an important contributor to the development of Western constitutional ideas, especially those of government with limited responsibility. He was one of the first medieval authors to advocate a form of church/state separation, greatly influenced the
Conciliar movement. This tract on heresy had the ultimate purpose to establish the possibility of papal heresy and to consider what action should be taken against a pope who had become a heretic. Ockham argued for complete separation of spiritual rule and earthly rule. He thought that the pope and churchmen have no right or grounds at all for secular rule like having property, citing 2 Timothy 2:4. That belongs solely to earthly rulers, who may also accuse the pope of crimes, if need be. After the
Fall he believed God had given humanity, including non-Christians, two powers: private ownership and the right to set their rulers, who should serve the interest of the people, not some special interests. Thus he preceded
Thomas Hobbes in formulating
social contract theory along with earlier scholars.
Logic In
logic, William of Ockham wrote down in words the formulae that would later be called
De Morgan's laws, and he pondered
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 19th and 20th centuries. His contributions to
semantics, especially to the maturing
theory of supposition, are still studied by logicians. William of Ockham was probably the first logician to treat empty terms in Aristotelian syllogistic effectively; he devised an empty term semantics that exactly fit the syllogistic. Specifically, an argument is valid according to Ockham's semantics if and only if it is valid according to
Prior Analytics.
Philosophy of Time William of Ockham believed that
eternity was exclusive to God. He rejected the concept of the
aevum as a special measure of duration of for angels. He also said it is not proper to call eternity a measure of duration. In Ockham's view, there was only one measure of duration, time, which was shared by all creation. == Theological thought ==