If you consult a number of authorities on what exactly metaphysics is, there will be as many different explanations of what it is as there are authorities. There will probably not be a lot of agreement about what metaphysics is, "supposed to be," (whoever the authority is that presumes to decide such things), but this metaphysics is only concerned with identifying what is meant by, existence, and, what it means to say something, exists; what is meant by reality, and, and what it means to say something is real: and what the nature of existence is that makes it knowable. The first two questions of metaphysics, "what is existence?" and, "what is reality?" belong to metaphysics proper. The third question, "what is the nature of existence?" belongs to a subset of metaphysics, ontology.
[NOTE: The word, "metaphysics," has unfortunately been adopted by an entire field of charlatans selling various mystic and superstitious notions that have nothing to do with the branch of philosophy called metaphysics. Such abominations as spiritualism, psychic powers, holism, and transcendentalism are all called metaphysical and some have actually corrupted philosophy itself. In general, even in philosophy, one must be very wary of anything called, "metaphysical."]
Existence, A Quality and A Thing
"To exist" means "to be." Anything that is, exists. Every physical object there is, every dream one is having, anything one is feeling, all knowledge, music, and events exist. There is nothing that does not exist. That does not mean that everything that exists does so in the same way or in the same manner. Obviously an automobile does not exist in the same way as a wish. The difference in the way things exist is very important and will be discussed under, "Modes of Existence," because modes determine what is and what is not real.
To say something exists means that it is. In that sense, existence is used as a quality. To say something exists means it has the quality existence. As a quality, existence is like any other, such as red or hot. Every red thing has the quality, "red," and every hot thing has the quality, "hot." If everything that exists were red we could say everything is red. We cannot say that about red, but, since nothing can be that does not have the quality existence, we can and must say, everything exists.
When "existence" is used to identify a "thing," what it identifies is everything with the quality existence. Existence is then a collective noun, like society, which means all the individuals that are the society. Existence, the thing, means everything that exists or everything there is.
That is why we can wave our arm, indicating the entire world, the heavens, the universe, and say, "this is existence," which is to say, "everything that is, is existence."
Existence, Known and Unknown
Existence (the thing) is everything that is, even if none or only some existents are known, perceived, or even suspected of being. A thing must actually be to exist but it is not necessary that anyone knows it is for it to exist.
Consciousness and knowledge exist and cannot exist without it being known by the individual whose consciousness and knowledge they are, of course, but there is almost nothing else that cannot exist without being perceived or known.
Modes of Existence
Earlier, I wrote: "Every physical object there is, every dream one is having, anything one is feeling, all knowledge, music, and events exist." These all exist, but there is something different in the manner in which they exist.
Things past may not exist now but, if they are things of the recent past that we remember, our memories of them do exist now; if they are things of the ancient past, any historical records of them exist now. Memories and history, however, do not exist in the same way you and I and the people, things, and events of today's news exist.
What exactly is the difference in the existence of dreams, feelings, knowledge, memories, history and the people and things of every day experience? The difference is called mode of existence.
[NOTE: Mode must not be confused with the absurd idea of "modality" which infects much modern metaphysics, and is an example of confusing ontology and epistemology]
Two Fundamental Modes Of Existence
The two fundamental modes of existence are material (or ontological) existence, and non-material (or epistemological) existence.
Material (Ontological) existence is all that exists independently of any human knowledge or awareness of that existence. "Independently of," does not mean, "separate from," but, "whether or not," any human is aware or has knowledge of that existence. The term material is used in this metaphysics somewhat differently than the common usage (which is usually the equivalent of, "physical). Here, material includes all physical entities, living organisms, conscious organisms, and human beings, because they all exist and have the nature they have independent of human knowledge or consciousness. Material or Ontological existence may also be referred to as natural existence, or just, nature.
Non-material (epistemological or psychological) existence includes everything that exists as the product of human minds and only in human consciousness. Epistemological existents include all concepts, all knowledge, all human developed knowledge methods including language, mathematics, and logic, as well as, the sciences, geography, history, philosophy, religion, literature (content), and arts.
Epistemological existents are contingent on human consciousness, volition, intellect, and reason and have no ontological existence and do not exist independently of human minds.
Modal Hierarchy Of Material Existence
The ultimate existence, without which there is no other existence is material existence. Material existence is what it is and has the nature it has whether or not anyone is conscious of that existence or knows what it's nature is. Material existence is the ultimate existence because it is not contingent on anything else. Nothing causes it, nothing is behind it, and nothing supports it.
Material existence has four aspects determined by the qualities that identify it. Those four aspects are 1. all physical qualities, 2. all life qualities, 3. all consciousness qualities, and, 4. all qualities of the human mind.
Though many philosophers only include physical qualities as, "material," since material existence is defined as that which exists and has the nature it has independently of human consciousness or knowledge, life, consciousness, and human minds exist materially, but, as attributes, not physically.
The physical aspects of material existence are all that can be consciously perceived, that is, seen, heard, felt, tasted, or smelled, including interoception, the perception of one's internal physiological states. The physical aspects of material existence are that which the physical sciences study. Since the qualities of life, consciousness, and mind cannot be directly perceived they are not physical and cannot be studied or explained in physical terms. The physical can all be explained in terms of the perceivable, directly, or indirectly (by the sciences, for example).
Ontology is the branch of philosophy that describes the nature of material existence, but it will be noted here that the four aspects of material existence are hierarchical. The physical qualities of existence are those that can be perceived. Life, consciousness, and mind cannot be perceived, but are perfectly natural qualities of some physical entities (organisms), just as the physical qualities are.
Life is a quality of some physical entities called organisms. Consciousness is a quality of some living organism, and minds are qualities of some conscious organism, that is, human beings. Mind can only be a quality of a conscious organism. Consciousness can only be a quality of a living organism. Life can only be a quality of a physical entity. There is no mind, consciousness, life, or physical attribute independent of the material existents they are the minds, consciousness, life, or physical qualities of.
Everything else that exists is non-material and the product of the human mind, including: all knowledge, languages, mathematics, logic, all science, technology, philosophy, history, literature, art, invention, and superstition (religion).
Materialism Vs. Physicalism
The branch of philosophy that identifies and describes material existence is ontology. Material existence is therefore referred to as ontological. Some philosophers confuse the terms metaphysical (which deals with all that exists) with ontology (which deals only with material existence). Metaphysically, everything exists; ontologically, only the material exists; and scientifically, only the physical exists.
[NOTE: There is no authority or mystic principle dictating how these distinctions must be made. I have used the terms metaphysical, ontological, and physical for these categories, other terms may be used so long as the difference in these concepts is made clear.]
Frequently, in everyday language, existence is used in a narrower sense meaning material existence, natural existence, or just nature. This common meaning of existence means everything we do, or can, directly perceive. The strict physicalist (sometimes called a materialist) believes that physical existence is all there is. If the strict physicalist were correct, physical existence and existence itself would be the same thing. The narrow meaning of existence is obviously wrong, else you and I and the people, things, and events of todays news would be all that exists; memories, history, language, and science, for example, simply would not exist.
There is much more than material existence. In addition to memories and history, there are dreams, imagination, and hallucinations. Someone somewhere, right now, is hallucinating, and that hallucination exists. History is just one branch of knowledge, but all our other knowledge also exists, including our knowledge of the sciences, technology, mathematics and philosophy. Every fictional character, place, or event that we write about, read about, or think about, exists so long as they are in somebody's mind or memory; but they are not material existents, they are psychological existents; but they are all real existents. They all exist, but all have different modes of existence.
Of course, fictional characters exist, but are they real?
Existence and Reality
Metaphysics is sometimes regarded as the study of reality. In that sense it answers the question, "what is real and what is the nature of the real and how is it distinguished from what is not real?"
The question in this form began with the original skeptics, the sophists, but became a serious part of philosophy by the influence of Plato, who introduced that subtle form of mysticism that has plagued philosophy ever since. That particular mystic idea is that what seems real and obvious is in some sense an illusion, while reality is something quite different and ultimately unknowable or knowable only by some means other than reasoning from the evidence. This is the view held by all mystics and championed by Kant.
This metaphysics dismisses all such mystical notions, but the distinction between reality and existence is still an important one, because, misunderstood, it produces much confusion in philosophy.
Reality Verses Existence
In one sense reality and existence refer to the same thing. They both refer to, "everything that is." But they are not the same concept. They identify the same thing; but, the intention or purpose of that identification is different.
The essential difference in these two words is this:
Existence refers to all that there is, without explicit reference to the nature of that which exists or the manner (mode) in which it exists;
Reality also refers to all that there is, but, explicitly or implicitly, includes in its meaning, the nature or mode of existence of the existents it includes.
Of the two concepts, existence and reality, existence is the broader term. I reiterate, everything that is, no matter what its nature or mode of existence, is included in the concept existence.
Reality includes everything that is, as well. It includes everything that is, but not in the same way existence does, as an unspecified collection of things, without regard to their nature, relationships, or mode of existence.
Reality includes every entity, every event, every quality, and every idea there is, but includes them as specific things with a specific nature and specific relationships to other things. Reality always specifies (explicitly or implicitly) the mode of existence. It includes fictional things as fictions, hallucinations as hallucinations, historical things as historical things, and material things as material things. Reality does not include fictions (such as Santa Claus) as material or historical facts because as material or historical facts they do not exist. It does include Santa Claus as a common fiction used for the enjoyment of children at the Christmas season—in that sense he really exists.
After reading Grimm's, "Billy Goats Gruff," to my grandson I quickly assured him, "trolls are not real." This is how we speak in everyday language.
The everyday concept of reality is derived from the fact we are conscious and are able to differentiate those things we are directly conscious of (perceptually) from all that we are conscious of "indirectly," as memories, imagination, dreams, or hallucinations. When we say this is real but that is only imaginary, we mean this is part of the world we have identified with those things we perceive directly, the physical, but that only exists as a perception created from material derived from memory. In everyday language, the real only includes the physical mode of existence.
This is the primitive concept of reality. It is the one most people mean when they use the word real, and for most purposes, it is adequate. In philosophy, however, this is not adequate and not quite correct. As fictional characters, trolls really do exist, it is as physical existents, trolls do not "really" exist.
For philosophical purposes, the primitive concept of reality must be expanded to include all things we are conscious of, differentiating the primitive concept of reality as "material reality" from the broader concept of reality, that includes all existents, both material and non-material. Reality includes everything included in the concept existence, but is more restrictive. Things exist no matter what their nature is; things are real only if the nature of their existence is specified and they "really" have that nature.
"Metaphysical language," here only refers to the language used within the discipline of metaphysics, not some language that itself could be called metaphysical. In this article, terms have been used that have very different meanings in other versions of metaphysics, which is why they have been carefully defined.
One of the reasons for the protracted treatment of words like, "material," "existence," and, "reality" for example, is because these words are continuously abused in philosophy and are always ambiguous whenever they are used. That does not mean that the way they are used in this metaphysics is the only way they can be used. If others choose to use those words differently there is nothing that says they must be used as they have been here, but they will not be very useful unless how they are being used is clearly explained. There is no authority determining such things.