Philosophical realism

Contemporary philosophical realism is the belief that our reality is completely ontologically independent of our conceptual schemes, linguistic practices, beliefs, etc. Philosophers who profess realism also typically believe that truth consists in a belief's correspondence to reality. Realism may be spoken of with respect to other minds, the past, the future, universals, mathematical entities (such as natural numbers), moral categories, the material world, or even thought.

Realists tend to believe that whatever we believe now is only an approximation of reality and that every new observation brings us closer to understanding reality. In its Kantian sense, realism is contrasted with idealism. In a contemporary sense, realism is contrasted with anti-realism, primarily in the philosophy of science.

History
The oldest use of the term "realism" appears in medieval scholastic interpretations and adaptations of Greek philosophy. Here, however, it is a Platonic realism developed out of debates over the problem of universals. Universals are terms or properties that can be applied to many things, such as "red", "beauty", "five", or "dog". Realism in this context, contrasted with conceptualism and nominalism, holds that such universals really exist, independently and somehow prior to the world. Moderate Realism holds that they exist, but only insofar as they are instantiated in specific things; they do not exist separately from the specific thing. Conceptualism holds that they exist, but only in the mind, while nominalism holds that universals do not "exist" at all but are no more than words (flatus voci) that describe specific objects.

The Scottish School of Common Sense Realism
Common Sense Realism or Scottish Common Sense Realism is a school of philosophy that sought to defend naive realism against philosophical paradox and scepticism, arguing that matters of common sense are within the reach of common understanding and that common-sense beliefs even govern the lives and thoughts of those who hold non-commonsensical beliefs. It originated in the ideas of the most prominent members of the Scottish School of Common Sense, Thomas Reid, Adam Ferguson and Dugald Stewart, during the 18th century Scottish Enlightenment and flourished in the late 18th and early 19th centuries in Scotland and America.

Its roots can be found in responses to such philosophers as John Locke, George Berkeley and David Hume. The approach was a response to the "ideal system" that began with Descartes' concept of the limitations of sense experience and led Locke and Hume to a skepticism that called religion and the evidence of the senses equally into question. The common sense realists found skepticism to be absurd and so contrary to common experience that it had to be rejected. They taught that ordinary experiences provide intuitively certain assurance of the existence of the self, of real objects that could be seen and felt and of certain "first principles" upon which sound morality and religious beliefs could be established. Its basic principle was enunciated by its founder and greatest figure, Thomas Reid:


 * "If there are certain principles, as I think there are, which the constitution of our nature leads us to believe, and which we are under a necessity to take for granted in the common concerns of life, without being able to give a reason for them--these are what we call the principles of common sense; and what is manifestly contrary to them, is what we call absurd.".

Reid argued strenuously against the notion that ideas, or sense-data, are the objects of perception at all; to wit, he rejected representationalism. One of his simplest arguments is that representationalism forces us to accept either skepticism or phenomenalism, which are both absurd, according to Reid; there surely is an external world, and we surely do have knowledge of it. So, by reductio ad absurdum, we must reject any theory that would force us to accept either skepticism or phenomenalism. Accordingly, we must reject representationalism, accepting that we do not perceive sense data at all. Someone looking at their hand does not immediately perceive a bundle or series of hand sense-data that represents the actual hand. Rather, they perceive the hand immediately and directly.

Edward S. Reed writes, e.g., "[Whereas] Thomas Reid wished to use common sense to develop philosophical wisdom, much of this school simply wanted to use common sense to attack any form of intellectual change." William Hamilton combined Reid's approach with the philosophy of Immanuel Kant. The school had considerable influence on philosophers elsewhere in Europe, Victor Cousin (1792–1867) being its most important proponent in France, and in the United States, exemplified by the American pragmatist Charles Sanders Peirce. Common Sense Realism swept American intellectual circles in the 19th century. James McCosh (1811–1894) brought it directly from Scotland 1868 when he became president of Princeton University, which soon became a major stronghold of the movement. Noah Porter (1811–1892) taught Common Sense Realism to generations of students at Yale. It greatly influenced conservative religious thought and was strongest at Princeton Seminary with the Princeton Theologians, and heavily influenced John Gresham Machen (1881–1937), a leader of the Fundamentalists in the 1920s. Much evangelical theology of the 21st century reflects Common Sense Realism.

In practice
Both these disputes are often carried out relative to some specific area: one might, for example, be a realist about physical matter but an anti-realist about ethics. The high necessity of specifying the area in which the claim is made has been increasingly acknowledged in recent years.

Increasingly these last disputes, too, are rejected as misleading, and some philosophers prefer to call the kind of realism espoused there "metaphysical realism," and eschew the whole debate in favour of simple "naturalism" or "natural realism", which is not so much a theory as the position that these debates are ill-conceived if not incoherent, and that there is no more to deciding what is really real than simply taking our words at face value.

Some realist philosophers prefer deflationary theories of truth to more traditional correspondence accounts.

Realism in logic and mathematics
Mathematical realism, like realism in general, holds that mathematical entities exist independently of the human mind. Thus humans do not invent mathematics, but rather discover it, and any other intelligent beings in the universe would presumably do the same. In this point of view, there is really one sort of mathematics that can be discovered: Triangles, for example, are real entities, not the creations of the human mind.

Many working mathematicians have been mathematical realists; they see themselves as discoverers of naturally occurring objects. Examples include Paul Erdős and Kurt Gödel. Gödel believed in an objective mathematical reality that could be perceived in a manner analogous to sense perception. Certain principles (e.g., for any two objects, there is a collection of objects consisting of precisely those two objects) could be directly seen to be true, but some conjectures, like the continuum hypothesis, might prove undecidable just on the basis of such principles. Gödel suggested that quasi-empirical methodology could be used to provide sufficient evidence to be able to reasonably assume such a conjecture.

Within realism, there are distinctions depending on what sort of existence one takes mathematical entities to have, and how we know about them.

Critics

 * Constructivist epistemology