Difference between Ontology and Epistemology

By: | Updated: Dec-5, 2017

Both “ontology” and “epistemology” are philosophical viewpoints that explain the complexities of daily existence and knowledge. While ontology and epistemology often go hand in hand, they are distinct concepts with their own set of definitions and theories. This article seeks to explain the fundamental differences that set these philosophical concepts apart.

Summary Table

A branch of philosophy involved in the study of reality and existenceA branch of philosophy that studies the nature of knowledge, its scope, and the methods used to acquire it
Makes use of principal questions such as, “What is existence?” “What is a thing?” or “What categories can one sort objects into that exist?”Asks questions such as “How do we acquire knowledge of thing?” or “How do we distinguish truthful ideas from false ones?”


comic expression
A comic expression of a basic ontological question

Ontology is the philosophical study of the nature of reality or existence, being, and becoming (i.e. change). It is traditionally considered a part of metaphysics and deals with questions about what objects exist or may possibly exist and how these entities may be categorized (where they belong within a hierarchy and how they are subgrouped according to their identifying characteristics). Ontology seeks to provide answers to questions that begin with the word “What.” The ultimate goal of this field of study is to understand if things exist or not. For instance, ontology works toward understanding questions such as “What is God?” “What happens after we die?” or “What is a hippopotamus?” In addition to answering the whats of existence, ontology is an attempt at explaining why something exists and how its being is related to other objects.

The word “ontology” is a compound word which combines the Greek words ontos (being) and logos (study). Parmenides, a fifth-century Greek philosopher, was one of the first to offer an ontological explanation of existence. He theorized that nothing comes from nothing, therefore existence is eternal.

While ontology, as a philosophical movement, is largely hypothetical, it has practical usage in the fields of science and technology. Placings objects in their respective categories is ontology. Drawing distinctions and determining whether something is an animal, tree, mineral, etc. is primary functions of ontology.


Epistemology is a fundamental branch of philosophy which deals with the theory and nature of knowledge, the rationality of belief, and justification. Most of the discourse in epistemology involves four areas, namely: the philosophical study of the nature of knowledge including how it interacts with such concepts such as truth, justification, and belief. The second and third areas deal with the problems posed by skepticism and the sources and scope of justified belief and knowledge. The last area is the basis of knowledge and justification.

In the nature of knowledge, philosophers believe there is a significant difference between knowing a concept, knowing how, and knowing by relation or association. A statement of belief is usually an expression of people’s faith in an entity, person, or authority – concepts which epistemology takes into serious consideration. This includes what people hold true from a cognitive standpoint. Thus, if a statement is known, then it categorically cannot be refuted as false.

Ontology vs Epistemology

So what’s the difference between ontology and epistemology? While it is considered a part of metaphysics, ontology is a branch of philosophy which involves itself in the study of the nature of reality and existence. Epistemology is also a branch of philosophy, but it is concerned with determining the nature of knowledge and all its aspects. Thus, ontology is about knowing what is true, while epistemology deals with the methods applied in knowing the truth.


Check out this YouTube video talking about ontology and epistemology.

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