ontology

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ontology summary

ontology

metaphysics

Written by Peter M. Simons

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Last Updated: Apr 2, 2025 • Article History

Key People:: Martin Heidegger; John Searle; George Santayana; Emmanuel Lévinas; Xiong Shili

Related Topics:: Occam’s razor; existence; individuation; essentialism; Being

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ontology, the philosophical study of being in general, or of what applies neutrally to everything that is real. It was called “first philosophy” by Aristotle in Book IV of his Metaphysics. The Latin term ontologia (“science of being”) was felicitously invented by the German philosopher Jacob Lorhard (Lorhardus) and first appeared in his work Ogdoas Scholastica (1st ed.) in 1606. It entered general circulation after being popularized by the German rationalist philosopher Christian Wolff in his Latin writings, especially Philosophia Prima sive Ontologia (1730; “First Philosophy or Ontology”).

History and scope

Wolff contrasted ontology, or general metaphysics, which applied to all things, with special metaphysical theories such as those of the soul, of bodies, or of God. Wolff claimed that ontology was an a priori discipline that could reveal the essences of things, a view strongly criticized later in the 18th century by David Hume and Immanuel Kant. In the early 20th century the term was adopted by the German founder of phenomenology, Edmund Husserl, who called Wolff’s general metaphysics “formal ontology” and contrasted it with special “regional ontologies,” such as the ontologies of nature, mathematics, mind, culture, and religion. After renewed criticism and eclipse under the antimetaphysical movement known as logical positivism, ontology was revived in the mid-20th century by the American philosopher W.V.O. Quine. By the end of the century, largely as the result of Quine’s work, it had regained its status as a central discipline of philosophy.

The history of ontology has consisted largely of a set of fundamental, often long-running and implacable disputes about what there is, accompanied by reflections about the discipline’s own methods, status, and fundamental concepts—e.g., being, existence, identity, essence, possibility, part, one, object, property, relation, fact, and world. In a typical ontological dispute, one group of philosophers affirms the existence of some category of object (realists), while another group denies that there are such things (antirealists). Such categories have included abstract or ideal Forms, universals, immaterial minds, a mind-independent world, possible but not actual objects, essences, free will, and God. Much of the history of philosophy is in fact a history of ontological disputes.

Methods

The methods of ontology vary according to the extent to which the ontologist wishes to rely upon other disciplines and the nature of the disciplines he wishes to rely upon. The most common method since the 20th century, the logical or linguistic method, relied upon theories of meaning or reference—as applied to either artificial logical languages or to natural languages—to dictate the kinds of entity that exist. Typically, lists of basic categories reflecting this method tended to correspond closely to broad linguistic (or syntactic) categories—e.g., substance (noun), property (adjective), relation (transitive verb), and state of affairs (sentence). A shortcoming of the logico-linguistic method, however, is that it is generally possible to change the ontology it produces by varying the semantic analysis of the natural or formal language in question.

Other ontological methods have been based on phenomenology (Husserl, Meinong), on the analysis of human existence, or Dasein (Martin Heidegger), and on epistemology. Husserl and Meinong contended that the basic categories of objects mirror the various kinds of mental activity by which they are grasped. Thus, there must be four basic kinds of objects corresponding to the mental activities of ideation, judgment, feeling, and desire. Heidegger held that it is a mistake to base the ontology of human existence on Aristotelian concepts such as matter and form, which are suitable only for artifacts.

The most widely used linguistic criterion of existence is due to Quine, who coined the slogan “To be is to be the value of a variable.” According to Quine, the propositions of a scientific theory should first be expressed in terms of predicate logic, or the predicate calculus, a logical language consisting of names, variables (which may be substituted for names), predicates (or properties), logical connectives (such as and, or, and if…then), and quantifiers. (Quantifiers can be combined with predicates and variables to form sentences equivalent to “Everything has such and such a property” and “There is at least one thing that has such and such a property.”) The scientific theory is then ontologically “committed” to those classes of entity whose members must be capable of replacing variables (i.e., capable of being the value of a variable) if the sentences of the theory are to be true.

Quine rejected any primacy for ontology, claiming that ontological categories should be suggested by natural science. Yet this did not prevent him from sometimes intervening on an apparently ad hoc basis to reduce the ontological commitments of classes of scientific theories to those of his minimal ontology of things and sets. His streamlining of scientific ontology to the minimum needed to keep the structure of scientific discourse intact led him to the doctrine of “ontological relativity,” according to which there is no privileged category of objects to which a given scientific theory is ontologically committed.

In contrast to Quine, philosophers such as Alfred North Whitehead (1861–1947) in England and David Armstrong in Australia regarded ontology as a core philosophical discipline that cannot depend to such a decisive extent on any other philosophical or scientific study. Its results can be evaluated only in terms of the adequacy of the overall system in the light of experience.

Peter M. Simons

Nature and scope of metaphysics

In the 4th century bce the Greek philosopher Aristotle wrote a treatise about what he variously called “first philosophy,” “first science,” “wisdom,” and “theology.” In the 1st century bce, an editor of his works gave that treatise the title Ta meta ta physika, which means, roughly, “the ones [i.e., books] after the ones about nature.” “The ones about nature” are those books that make up what is today called Aristotle’s Physics, as well other writings of his on the natural world. The Physics is not about the quantitative science now called physics; instead, it concerns philosophical problems about sensible and mutable (i.e., physical) objects. The title Ta meta ta physika probably conveyed the editor’s opinion that students of Aristotle’s philosophy should begin their study of first philosophy only after they had mastered the Physics. The Latin singular noun metaphysica was derived from the Greek title and used both as the title of Aristotle’s treatise and as the name of its subject matter. Accordingly, metaphysica is the root of the words for metaphysics in almost all western European languages (e.g., metaphysics, la métaphysique, die Metaphysik).

Aristotle provided two definitions of first philosophy: the study of “being as such” (i.e., the nature of being, or what it is for a thing to be or to exist) and the study of “the first causes of things” (i.e., their original or primary causes). The relation between these two definitions is a much-debated question. Whatever its answer may be, however, it is clear that the subject matter of what is today called metaphysics cannot be identified with that of Aristotle’s Metaphysics. While it is certainly true that all the problems that Aristotle considered in his treatise are still said to belong to metaphysics, since at least the 17th century the word metaphysics has been applied to a much wider range of questions. Indeed, if Aristotle were somehow able to examine a present-day textbook on metaphysics, he would classify much of its content not as metaphysics but as physics, as he understood the latter term. To take only one example, the modern book would almost certainly contain a great deal of discussion of philosophical problems regarding the identity of material objects (i.e., the conditions under which material objects are numerically the same as, or different from, each other; see below Problems in metaphysics: Identity). An ancient example of such a problem is the following: A statue is formed by pouring molten gold into a certain mold. The statue is then melted down and the molten gold poured into the same mold and allowed to cool and solidify. Is the resulting statue the same statue as the original? Such problems evidently do not concern (at least not directly) either being as such or the first causes of things.

The question of why modern metaphysics is a much broader field than the one conceived by Aristotle is not easy to answer. Some partial or contributing causes, however, may be the following.

1. The appropriation of the word physics by the quantitative science that now bears that name, with the result that some problems that Aristotle would have regarded as belonging to “physics” could no longer be so classified. As regards the problem of the gold statue, for example, modern physics can explain why the melting point of gold is lower than the melting point of iron, but it has nothing to say about the identity of recast statues. (It should be pointed out that metaphysicians are not interested in recast statues—or any other remade physical object—as such. Rather, they use such examples to pose very general and abstract questions about time, change, composition, and identity and as illustrations of the application of principles that may govern those concepts.)

2. Similarity of method between Aristotelian and modern metaphysics. The American philosopher William James (1842–1910) said, “Metaphysics means only an unusually obstinate attempt to think clearly and consistently.” That is not a bad statement of the only method that is available to students of metaphysics in either its original Aristotelian sense or in its more recent extended sense. If one is interested in questions about the nature of being, the first causes of things, the identity of physical objects, or the nature of causation (the last two problems belong to metaphysics in its modern sense but not its original sense), one will find that the only method available is an “obstinate attempt to think clearly and consistently” about them. (Perhaps, indeed, this is the only method available in any branch of philosophy.)

3. Overlap of subject matter between Aristotelian metaphysics and Aristotelian physics. The topics “being as such” and “the first causes of things” cannot be wholly divorced from philosophical problems about sensible and mutable objects, the original subject matter of Aristotle’s physics. Sensible and mutable objects, after all, are—that is, they exist—and, if indeed there are first causes of things, they certainly stand in causal relations to those first causes.

Whatever the reasons may be, the set of problems to which the word metaphysics now applies is so diverse that it is very hard to frame a definition that adequately expresses the nature and scope of the discipline. Such traditional definitions as “an investigation into the nature of being,” “an attempt to describe the reality that lies behind all appearances,” and “an investigation into the first principles of things” are not only vague and barely informative but also positively inaccurate: each of them is either too broad (it can be applied just as plausibly to philosophical disciplines other than metaphysics) or too narrow (it cannot be applied to some problems that are paradigmatically metaphysical). Thus, the only way to give a useful account of the nature and scope of metaphysics as the term is now understood is to provide a survey of a series of philosophical problems that uncontroversially belong to modern metaphysics. That survey follows.