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The conventional view of reality[1] is grounded upon perceptions of the world as we experience it, and reflection concerning such perception. This view is related to, but not identical with, empiricism. Perspectives depend upon a particular point of view. There could be as many perspectives as there are people. However, because reality relies to some extent on shared understanding concerning individual perceptions, reality falls within convention. Views of reality have greater or lesser degrees of refinement and organization. Some are highly systematized, for example, scientific theories that use specialized methods to verify their findings, and other views are based upon mores or societal institutions.

Because of the regress problem, establishing a foundation of truth and reality is a problematic that underlies all disciplines, including mathematics. The regress problem (in a nutshell) is that every proposition rests upon premises, which in turn are based upon underlying premises, and so on. Thus, the underlying reality is subject to regress.[2] The desire to establish an underlying ground of all or part of reality, that is, to say what reality "really is," has been a long-standing preoccupation of philosophy and the sciences.

Platonic Realism

Plato's philosophy concerns the nature of Being itself, "what is" ; it distinguishes between "what is" and material existence. What is Real is "what is" in itself; for Plato, these are the 'Forms'. Here is derived the term "Platonic Realism" which refers to a view of reality that grounds truth (the ultimate Reality) in a Being (the Forms) outside sensible reality, and beyond the Forms in the Good that is beyond Being. The Platonic Theory of Forms does not depend on sensible perception to ascertain truth but on another form of 'seeing' that is only possible for the soul [Ψυχή]. In the myth of the charioteer, Plato argues, "For a human being must understand a general conception formed by collecting into a unity by means of reason the many perceptions of the senses; and this is a recollection of those things which our soul once beheld, when it journeyed with God and, lifting its vision above the things which we now say exist, rose up into real being" (249c).[3]

In Plato, Being is itself and nothing but itself. Thus, the Form of Justice is simply Justice itself. To define, we use predicates, but a Form would have no predicates in the usual sense of such things insofar as a Form's definition would give you something that has the same thing on either side of the equation such that Justice=Justice. No matter what predicates you add to a thing itself [the Form], for Plato, it remains the same. On the other hand, when we say that Mary has blue eyes and Bill has brown eyes, we refer to items pertaining to sensibility and particular biological traits. It is a trait of sensible reality to be changeable. Plato holds to the idea of an unchangeable reality that underlies the world of experience.

Given his definition of Reality, it is easier to see why, for Plato, knowledge is not 'acquired', but involves anamnesis, that is, the recollection of the Ideas, which the soul had known in a previous existence, especially by means of reasoning. Real knowledge involves a vision of the shining of the Beautiful, its Eidos. For one thing, how would we bring something immutable into material life, such that we could acquire it? For another, would we acquire the Being of the Beautiful or merely another image of the Beautiful? Conversely, the objects of immanent, sensible experience remind us of the things themselves: we see a bed, and this evokes the Idea of a bed, and so on. Knowledge is the extent to which you can connect the bed of experience to the immutable Form of the bed (597a-598b).[4]

So there is a Form of the relation between numbers, the Form of specific numbers, and the Form of the abstraction of 'number' itself. In immanent existence, these forms are all mixed up in matter and predicates abound. But what of the varying degree to which some of us are able to make these relations, to gain knowledge? I may see a beetle climbing on a branch and think about bugs. If I am no entomologist I may not go to the specific Form of 'beetle', only the form of a beetle in general. My inability to understand the intricacy of number does not prevent me from a vision of the form of 'number' in general or its abstraction, but may prevent me from seeing the intricacy of their relationships.

Because the Forms are external to the sensible copies of reality, it does not seem that there can be change in something like Beauty or Justice. Immanent life seems to confirm the finding that objects of sensation appear to be all mixed up together. We see justice and truth in varying degrees, as composed in matter, rather than by themselves. These break, degrade, disperse or scatter. Material things have parts whereas immaterial things do not. Plato's explanation is that the beautiful we experience is beautiful because it participates in the Form of Beauty, not because it is beautiful in itself. Accordingly, if I want to know if a sunset is beautiful, I go to the Form that gives the sunset its beauty. The relation of the particular sunset to Beauty remains temporary (the sun goes down, although the beauty of the sunset cannot fade). Perception of beauty in this world involves establishing such a relationship between objects of sensation and that which is truly Beautiful. Unlike finite beauty, the Form of the Beautiful has no beginning or end (when we perceive the beautiful sunset as being present, we are soon dissuaded of this reality when we perceive that the facts have changed and are now otherwise once the sun goes down).

Further, to understand Plato's conception of Reality, we must get around the idea of causality. The Real does not come to be and cease to be in a material causal sense. The scientific cause of the 'appearance' of a sunset, the appearance that the sun moves, for us has to do with the movements of bodies in space but from a Platonic view implies a connection to the Form that is the underlying cause of the sun or of a sunset seen in in our experience. The bond to the Beautiful of the sunset or to the Form of the sun itself is real, but the objects we think of as sun or sunset do not amount to things in themselves. All we have done in locating these objects is to establish a relation to Reality.

Conventional reality, for Plato, is unsatisfactory, and knowledge of this type of reality can be categorized as doxa, the stuff of beliefs and opinions, rather than the act of real knowledge. Yet it should not be concluded that Plato rejects doxa. Including "geometry and the kindred arts," Plato asserts that, through the power of dialectic (as he conceives of it), reason can treat "its assumptions not as absolute beginnings but literally as hypotheses, underpinnings, footings, and springboards so to speak" (511b)[4].


Religion commonly ties reality to the notion of the divine. Thomas Aquinas, for example, says that statements about everyday reality are true of God only metaphorically. Similar ideas can be found in Buddhist traditions. each species belongs its own mode of perfection and being. The same is true of whatever names designate the properties of things, which are caused by the proper principles of their species. Hence, they can be said of God only metaphorically. But the names that express such perfections along with the mode of supereminence with which they belong to God are said of God alone. ... Thomas Aquinas[5]

To aid in interpretation of these remarks, we have:

It is not too much to say that, for Thomas, as for Aristotle, the forms in the natural world attain an altogether higher level of reality in our minds – because, as already for Aristotle, the world constitutes an intelligible whole in virtue of its dependence upon the divine mind. ... Fergus Kerr[6]

Model-dependent realism

See also Model-dependent realism.

Platonic realism described above introduces the idea of the soul and its journey with God—subjecting Plato's approach to a possible interpretation of supernaturalism. Some philosophers think that everything that exists we can only apprehend as constructs of our mind, what might be termed an anti-realist or idealist point of view, that external perception consists of ideas. In contrast, classical science adopts a realist point of view, that objects of sense perception have an existence independent of the act of perception. Modern science is somewhat in the middle, proposing reality as indefinite to a degree, governed by chance in some particulars, and becoming definite only upon human observation.

The physicists, Stephen W. Hawking and Leonard Mlodinow, in their book, The Grand Design, offer a concept called model-dependent realism that they believe skirts the difficulties arising from those differing views.[7]

A few excerpts from Hawking's and Mlodinow's book describe the basics of model-dependent realism:

Model-dependent realism short circuits all this argument and discussion between the realist and anti-realist schools of thought. According to model-dependent realism, it is pointless to ask whether a model is real, only whether it agrees with observation. If there are two models that both agree with observation,...then one cannot say that one is more real than another. (pp. 45-46)

...model-dependent based on the idea that our brains interpret the input from our sensory organs by making a model of the world. When such a model is successful at explaining events, we tend to attribute to it, and to the elements and concepts that constitute it, the quality of reality or absolute truth...(p. 7)

But there may be different ways in which one could model the same physical situation, with each employing different fundamental elements and concepts. If two such physical theories or models accurately predict the same events, one cannot be said to be more real than the other; rather, we are free to use whichever model is most convenient...(p. 7)

It might be that to describe the universe, we have to employ different theories in different situations. Each theory may have its own version of reality, but according to model-dependent realism, that is acceptable so long as the theories agree in their predictions whenever they overlap, that is, whenever they can both be applied... (p. 117)

We make models in science, but we also make them in everyday life. Model-dependent realism applies not only to scientific models but also to the conscious and subconscious mental models we all create in order to interpret and understand the everyday world. (p. 46)

Hawking and Mlodinow assert that argument over the existence or nature of objective reality is pointless, and argument should be focused instead upon models and their success in according with observation and in predicting new observable phenomena. They do agree that such success induces a tendency in scientists to "attribute" to theories the quality of reality, but point out that overlapping theories may use different but equally valid concepts and structures to explain the same observations. Thus, subscribers to model-dependent realism would not assert that models must provide a unique picture of reality (several different pictures of reality may accord with same observations). Nor would they assert that models incorporate every available observation (the totality of observations may require a network of overlapping models).[7]

The article, model-dependent realism, provides an extended discussion of this topic, and a discussion of the published reactions to it.


  1. The New Oxford American Dictionary gives this definition of reality: 1. the world or the state of things as they actually exist, as opposed to an idealistic or notional idea of them: he refuses to face reality | Laura was losing touch with reality. | 2. (Philosophy) existence that is absolute, self-sufficient, or objective, and not subject to human decisions or conventions. (2010) Angus Stevenson and Christine A. Lindberg, eds.: New Oxford American Dictionary, 3rd ed. Oxford University Press. ISBN 0195392884. 
  2. Scott Aikin (2011). Epistemology and the Regress Problem, Routledge Studies in Contemporary Philosophy. Routledge. ISBN 0415878004. 
  3. Plato (1999). Plato: Euthyphro. Apology. Crito. Phaedo. Phaedrus, Loeb Classical Library ed. Harvard University Press. ISBN 978-0-674-99040-1.  Macmillan edition of 1892 at Google books.}}
  4. 4.0 4.1 Plato (2005). Edith Hamilton and Huntington Cairns, eds: The Collected Dialogues of Plato: Including the Letters, Bollingen Series LXXI. Princeton University Press. ISBN 978-0-691-09718-3. 
  5. Thomas Aquinas. Anton C Pegis, translator:Chapter 30: The names that can be predicated of God; §2. Contra Gentiles: Book One: God. Retrieved on 2011-10-13.Joseph Kenney, O.P. website}}
  6. Fergus Kerr (2009). Thomas Aquinas: a very short introduction, Volume 214 of Very short introductions. Oxford University Press, p. 61. ISBN 0199556644. 
  7. 7.0 7.1 Hawking SW, Mlodinow L. (2010). The Grand Design, Kindle edition. New York: Bantam Books. ISBN 978-0-553-90707-0.