I know that ontology is a sub-field of metaphysics. But I can't see the difference between them. I mean ontology is defined as "The study of being and existence", and metaphysics is defined as "fundamental nature of being and the world"; is there a difference between these two definitions?

  • As you say, really there is no difference. We may choose to study this or that area of metaphysics but by its very nature all the approaches to metaphysics converge. It would not be possible to solve ontology without solving all significant metaphysical problems. There is a difference between the definitions but as you observe it doesn't matter much.
    – user20253
    Commented Oct 20, 2017 at 13:27
  • The difference is that ontology (the study of being) does not have to be studied metaphysically. For example, M. Foucault pursued an 'historical ontology of ourselves' which was opposed to metaphysical (or essential) claims. Commented Jun 11, 2020 at 19:27

9 Answers 9


This is an excellent question, and deserves more discussion than I can really provide here, but I'll try to give a simple and clear delineation between the two fields.

Metaphysics is a very broad field, and metaphysicians attempt to answer questions about how the world is. Ontology is a related sub-field, partially within metaphysics, that answers questions of what things exist in the world. An ontology posits which entities exist in the world. So, while a metaphysics may include an implicit ontology (which means, how your theory describes the world may imply specific things in the world), they are not necessary the same field of study.

Let's consider an example that might clarify the distinction a little more: gravity. Gravity is certainly not an object, but I assume that physics would be in a pretty bad spot if we say that gravity isn't real. So what should we make of gravity? Well, we roughly know that gravity is a physical law that affects matter.

So, a metaphysical conclusion we can draw from this is:

"The world is such that matter is governed by physical laws."

This is a metaphysical conclusion because it describes a way that reality is - laws are a property of reality (and further, reality is the kind of reality that can have laws). The distinct ontological conclusion to draw from our discussion so far is:

"There is a physical law of gravity."͏͏͏͏͏͏

This is ontological because it is about a posited entity - the entity that we call "the law of gravity". Now, where most people seem to get tripped up here is in the fact that our ontological conclusion is also a metaphysical conclusion; any posited entities are also part of (or describe) how the world may or may not be. But the ontological conclusion differs from the non-ontological metaphysical conclusion insofar as it may imply metaphysical conclusions, but is not itself about reality. "Meta" means roughly "about" or "after", and physics means physics, so metaphysics means "about (or after/beyond) reality". The ontological conclusion is about a given entity (or kind of entities).

I hope that helps!

  • 2
    This answer was helpful but I got confused when you said a law "exists". What if a physical law is just a description of how things work, wouldn't that bump it out of ontology back into the broader category of metaphysics? Otherwise it seems like we could reify any behavior and make it sound ontological?
    – Benjamin
    Commented Jun 12, 2012 at 23:52
  • 1
    Its does but I got confuse when you said the sentence 'the world is governed by physical laws' is a metaphysical conclusion, since the law of gravity is a physical thing. Please explain.
    – user14950
    Commented Jun 11, 2015 at 2:29
  • I just want to comment on your metaphysics etymology position: the word "meta" does mean "after", but the name "metaphysics" appeared because the Aristotle works about this subject were arranged after the works on physics. That's all. (a lot of people's other meanings were fabricated only after)
    – cripox
    Commented Dec 9, 2019 at 17:09
  • The law of gravity does not exist, ontologically. Read Newton. He admits in the Principia that he does not know what causes gravity. Only that he can measure the affect. Later Einstein admitted that he needed to read Hume to publish his theories on relativity: Hume showed that there is no Cause and effect: they are products of Custom and Habit and thus imposed on the world by the mind. Thus your answer demonstrates an appalling philosophical ignorance.
    – Rob
    Commented Dec 26, 2019 at 4:04


generally covers topics such as cosmology (space and time), determinism and free will, mind and matter, ontology (being, existence, reality), necessity and possibility, identity and change, among others.


is just one of those subtopics of metaphysics; it focuses on the categories of being and whether things can be said to exist or not.

The Wikipedia articles on Metaphysics and Ontology are not entirely clear but you can get an idea of the differences by looking over each. The SEP article on Metaphysics (and ontology) is more in-depth and I would definitely recommend it if you want a thorough overview, especially since someone seems to want to vandalize the Wikipedia Ontology page...

  • 1
    Wow. I rarely frequent the Wikipedia philosophy pages (preferring the SEP and IEP) but it never occurred to me that "Ontology" would be an attractive target for Wikipedia vandals. (Good answer, btw.) Commented Oct 28, 2011 at 6:54
  • 1
    Yeah, actually I thought it might be from someone here... according to a few ip traces, it's someone from Milwaukee. Anyone here from Wisconsin? *looks around* :P
    – stoicfury
    Commented Oct 28, 2011 at 14:50
  • @stoicfury, What about ontology vs number theory?
    – Pacerier
    Commented Oct 18, 2017 at 12:15

Your confusion is justly warranted because metaphysics turns out to be a very broad field and is somewhat difficult to define (if at all possible). Traditionally metaphysics has been divided into two parts: special metaphysics and general metaphysics. Ontology was included under the umbrella of general metaphysics, which traces its roots back to Aristotle, and can be thought of what comes after- physics, the things beyond the physical. (The Greek word for "after" is "meta"). But things included under the umbrella of special metaphysics came historically after general metaphysics and includes the possibility of free will, the nature of identity, the existence of God, etc.

So in short, ontology is a sub-field of metaphysics. Ontology is the study of being, and is a little more specific and narrow than metaphysics in general which is the study of the general nature of reality, and this includes other questions more broad and fundamental than those of ontology alone. You might find this link helpful: Metaphysics or Ontology?

  • 2
    It is worth noting that Aristotle never used the word "metaphysics". The title of Aristotle's metaphysics was applied by later collators and was simply applied because (as you note) it came after his Physics. This is not to say that it is somehow beyond physics, but merely an ordering of works in a collection. Much like chapter 2 follows chapter 1 in standard ordering of chapters. Only after Aristotle did people read anything into this ordering.
    – Dennis
    Commented Feb 2, 2013 at 5:20

When it comes to thought on metaphysics, the only way someone can clarify what the formal or modal distinction between the two are is if one considers the completed sub-disciplines of metaphysics, i.e. what it is a metaphysician does well or non-well in the field of metaphysics. Metaphysics is comprised of the following;

  • Ontology
  • Mereology
  • Protothetics
  • Morphology

The other disciplines of philosophy play a significant role in the practice of any of these sub-disciplines. Ontology is the "logic of being", whereas mereology is the "logic of parts(existential to being)", protothetics is more of a "calculus and proof" of the two aforementioned truth-values, whether they are veritable formulations, whereby morphology is the "logic of forms", their after been proven dynamisms.

So to speak this is metaphysics in a nutshell, however, be mindful of metaphysicians play of these sub-disciplines, their play in practice depends alot on whether a metaphysician is "doing well" in metaphysics. Philosophy has a long history of stupidity.


Perhaps we should really find out when metaphysics started as a discipline distinct from other disciplines, and by discipline I understand a study by man of things whatsoever at any time in any environment under any aspect whether real or unreal or purely fictional, possible or impossible or even endowed with contradictory features whatever, in objective reality or merely in the mind of man.

On that basis I would say that metaphysics acquired a specific distinction from all other disciplines when man notices that there is a difference between something and nothing, and seeks to draw up the features of something by which something is different from nothing.

At this point I would imagine ontology came about as a distinct study of mankind separate from metaphysics, because it is concerned with the kinds of something which something is already no longer nothing.

But in actual usage the two terms are used inter-changeably.

For example with atheist cosmologists, they want to understand nothing as something, but it is their ruse in order to tell common atheists who do not think deeply: that the universe came forth from nothing: so, no God is needed.

In that respect they are already into a wrong metaphysics and a wrong ontology, and man cannot draw that conclusion of their being wrong, unless he is cognizant of what is metaphysics and ontology and what is any other study of man distinct from metaphysics and ontology, and also the distinction between metaphysics and ontology.

Now, with theist cosmologists, the correct metaphysics is that there has always been something even before the varieties of something came to the notice of man; and the always something is God, the only self-existing something that is in effect the unique uncreated creator and operator of the created universe,in His fundamental relation to the universe that is studied by scientists or more in particular material scientists.

That is why atheist thinkers do not go for metaphysics and ontology and all kinds of philosophy, they just keep on insisting that material things are the only somethings to study for man.

But even the science of physics which is a material investigation of the ultimate particles and origin of the (material) universe is today cognizant of the fact that the material universe has a beginning 13.7 billion years ago.


I hope I'm not over-simplifying... According to what I understood from my philosophy teacher, metaphysics is comprised of three fields:

  1. Ontology - discourse of that which exists,
  2. Epistemology - discourse of what we can know,
  3. Ethics - discourse of that which follows (for human behavior)

This distinction is useful, such as for discussing that...

  • Heidegger accuses philosophers since Socrates of moving too fast past the "existential" (ontology, Being).

  • Levinas accuses Heidegger of placing ontology over ethics, with disastrous historical consequences.

Source: "Totality and Infinity" by E. Levinas, p.46f

  • Epistemology and Ethics (in Philosophy of Values) are not part of Metaphysics, but are considered siblings, all parts of Philosophy.
    – cripox
    Commented May 6, 2019 at 23:46
  • Epistemology and Ethics are considered part of metaphysics. It would not be possible to study metaphysics and avoid these areas.
    – user20253
    Commented Apr 27, 2020 at 13:18
  1. Ontology is the study of existence, and like any study where falsifiable and verifiable hypotheses can be formulated to advance knowledge claims, ontology is heuristic. Where there is knowledge to be obtained by means of studying existence, there can be philosophy - the respect for obtaining knowledge.

  2. Metaphysics are nothing more than unjustifiable descriptions, speculations regarding imponderables, and the conclusions issued from them little more than opinion and solicitation to agreement, i.e. metaphysics are hermeneutical, and hence no knowledge is to be obtained, therefore metaphysics are irrelevant to philosophy.

The morphology of the term ontology sums it up: ontos- + -logia, i.e. the study of that which is.

The morphology of the term metaphysics is, on the other hand wholly misleading: meta- + physics - as if there were something "above" or "beyond" physics. In the sense of meta- as "self-referential" or "about", there is nothing in metaphysical discourse which is not otherwise adequately and heuristically addressed by the philosophy of language, philosophy of science, and the philosophy of consciousness.

Furthermore, the term metaphysics comes to us by way of misinterpreting a portmanteau derived from Andronicus of Rhodes' "ta meta ta phusika" (i.e 'the things after the Physics') used while categorizing the extant writings of Aristotle. Lacking a significantly coherent statement in the beginning of the writings to work with, as would have been customary for a title in his day, Rhodes' organizing principle for these works of Aristotle (essentially categorizing Aristotle's hodgepodge into a collection) was simply that they were placed on the shelf after Aristotle's books on physics as "ta meta ta physika biblia" i.e. "the books that come after the books on physics." Only later was this categorical placeholder naming considered taxonomic and thus began a pernicious history of metaphysicians soliciting agreement with weltanschauung and proffering the hermeneutical as if it were heuristic - all under the banner and misnomer of "philosophy" i.e. love of wisdom; read: respect for obtaining knowledge; i.e. empirical verification of what is, not what is to [you; me; us; or, them]

  • @ Mr. Kennedy All philosophy is Hermeneutics. The abstractions brought forth are interpretations. The resulting connections to behaviors and actions are physical manifestations of these interpretations. And - I'd alter your summations to be - *Ontology is making the abstractions for 'being' a subject for inquiry. Metaphysics is connecting those abstractions of 'being' to the physical plane. Commented Nov 17, 2018 at 14:37
  • @NormanEdward Philosophy is neither debate nor hermeneutics, nor are the propositions comprising it settled by articulation of sentiment (agreement or disagreement).The propositions of hermeneutic metaphysicians from pre-Socratics extant is akin to poetry, not philosophy. Wisdom obtains knowledge. Hermeneutics neither obtains knowledge nor advances knowledge claims. Philosophy is love of wisdom, and this meaning has stood 2500+ years despite the modern misnomer for "my opinion", "a way of looking at things", "weltanschauung", et cetera.
    – MmmHmm
    Commented Nov 17, 2018 at 19:03
  • I agree with many of your points and I am not debating you. Dialogues are much more beneficial to 'gaining wisdom' since the goal is to reach beyond what is already within your grasp. And that correlates to hermeneutics, (not argument or disagreement) with the connections of ideas through context and into shared distinctions. You may view that as my opinion. I thank you for your response. (I am fairly sure that there were a multitude of sources for that coalesced into ideas expressed today as coming from Plato, Socrates, Aristotle, etc. That is an opinion.) Commented Nov 18, 2018 at 5:08

The discussion between metaphysics and ontology is crucial because what we are most concerned about is ‘why there is something rather than nothing.’ An easy distinction between metaphysics and ontology can be drawn if we take metaphysical principles to stand for those entities which do not have a specific referring entity in the empirical world and ontological principles are those entities which have a one-to-one referring entity in the empirical world. For example God is a metaphysical principle because god does not have a referring entity in the empirical world. The idea of a table is ontological because it has a referring entity in the empirical world. This is the reason why the famous existentialist philosopher Martin Heidegger moved away from Metaphysics and took recourse in Ontology to give a better meaning and grasp of philosophy.

  • First off welcome to philosophy.se. This is indeed how Heidegger uses the terms but plenty of other people use the terms differently...
    – virmaior
    Commented Oct 31, 2014 at 14:03
  • Why there is something rather than nothing; maybe a more accurate question might be 'Why there is something rather than a 'state of affairs' where no 'sentient being can ask questions like this one?
    – 201044
    Commented Jun 24, 2015 at 3:03

Just my opinion on a popular question: ontology asks about 'existence' (what exists and how?), whereas metaphysics asks questions about the things that we assume exist (what is identity?).

That allows for overlap, so when we ask about the Being of man that is both ontological and metaphysical.

I assume the question is asking about different philosophical tendencies, rather than an incomplete list of ontological vs metaphysical problems and arguments

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