Reality

The conventional view of reality 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. 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).

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, since a Form's definition would give you something that has the same thing on either side 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.

Given his definition of Reality, it is easier to see why, for Plato, knowledge is not 'acquired', but involves anamnesis. 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).

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 this, finding because 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. 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 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 all 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).

Religion

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.

...to 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

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

Model-dependent realism

See also Model-dependent reality.

The Platonic approach described above is of very broad scope. A much more restricted concept of "reality" in science is limited to the explanations of observations or measurements, probably a view of reality that Plato would discount. Plato would require that "reality" transcends any feeble attempt to confine it to a particular set of observations, particularly as this reality changes with the introduction of additional observations admitted to explanation as technology evolves. Recently the connection of theory to reality has been explored by physicists Stephen W. Hawking and Leonard Mlodinow. In their book, The Grand Design, they propose a model-dependent reality, which refers to a model or picture consisting of the combination of any set of observations accompanied by theoretical concepts that explain and connect those observations. Such a model-dependent reality need be neither unique (several explanations of a set of data may work), nor need it cover every available observation (the totality of observations may require a network of overlapping model-dependent realities).

The question of comparing or classifying competing model-dependent realities that cover the same ground arises, although such issues are independent of the concept itself, and may involve subjective considerations. Hawking/Mlodinov do not address the intuitive qualities of a model, but they do raise the question of what constitutes a good model. They suggest a "good model" has these characteristics:(p. 51)

1. It is elegant
2. Contains few arbitrary or adjustable elements
3. Agrees with and explains all existing observations
4. Makes detailed predictions about future observations that can disprove or falsify the model if they are not borne out.

These desiderata of a "good model" allow critique of different models that are equal from the stance of model-dependent reality by itself. If these "principles of comparison" have indeed any justification outside of their general acceptance, these lie outside the tenets of model-dependent reality.