Truth is a concept as old as reality and both are a backbone of philosophical discussion. As with the conceptions of reality that have occupied thinkers for over two millennia, truth and its contention has a rich and diverse history. So what are the best theories of truth? Should we think about truth as a monolithic concept or as a pluralistic one? What about truth in the humanities compared to the sciences? And how can we deal with the potential of ultimate truth concerning meta-pictures of overall reality and existence?
Today, a popular version of truth is the correspondence theory of truth. Here truth corresponds to verifiable facts about the world such as today's date. Unsurprisingly this framework of truth is often found in a realist account of truth - particularly in philosophy of science. This framework of truth is simple to understand and it forms a technical part of truth in philosophy as well as general everyday assumptions about truth. Despite its simple and common palatability it is problematic. If truth corresponds to a set of externally verifiable facts about the world such as today's date then it begs the question of what constitutes a fact. As the renowned philosopher Simon Blackburn said to me "What are facts? You cannot touch them or move them around". Furthermore an anti-realist could argue that the constitution of an empirically observable fact is theory dependent and therefore not only does that question the immediate validity regarding the constitution of a verifiable fact outside the landscape of the theory in question but also the constitution of truth in different theories throughout history that have tried to explain the same phenomena. For instance Newton and Einstein's theory of gravity have different accounts of what gravity truly is and this is a position often advanced by moderate anti-realists. The extreme anti realist may deny the very possibility of an external objective truth in epistemological and ontological terms.
The correspondence theory of truth and its mirror counterpart of anti-realism can be too extreme for some thinkers and a middle ground can be found in pragmatism. Pragmatism attempts to marry aspects of the realist position with aspects of anti-realism by utilizing the correspondence to external facts like today's date with the consideration of the psychological construction of the world such as theories and their accompanying beliefs - in this example the theory of the calendar year. The pragmatist strikes a balance by arguing that we theoretically construct the world around us but that the theories we build can be empirically verified in one way or another. For the pragmatist truth lies in the correspondence to empirical observation coupled with the psychological construction of the world.
However could it be that the problems encompassing truth occur because we are treating truth as a monolithic concept when perhaps it should be a pluralistic one? Is truth simply not just truth or can it be argued that what constitutes truth in mathematics is not the same as what constitutes truth in language, the arts and even scientific theories? The pluralistic version of truth argues in this way. It allows us to think in a more structured way about how different domains of inquiry have different definitions of what constitutes truth. According to Michel Lynch, a leading philosopher in this area, what unites truth is its function. The one universally applicable category of truth is that it serves a function and this is the only definition that all forms of truth have in common. How truth is constituted in different fields of inquiry is often specific to that form of inquiry. It must be noted that this is not a postmodernist version of truth; that there is no objective truth that exists in itself and that truth is merely a subjectively formed concept of the inquiring mind rationally justified by discourses, which were postmodernist ideas propagated by the likes of Foucault and Derrida. Instead it is not that objective truth is not possible but that there is no universal form regarding the actual concept of truth, only how it functions in different areas. This allows us to permit that truth in mathematics, which often involves analytic truths by definition, is different from a truth in literature and a truth in science.
Those who believe that the only way truth can be understood is through empirically testable science are often tempted to say that of course no truth exists in the humanities and only in science because science is objective and the humanities is merely subjective opinion deliberated through rational argumentation. However even if the foundational principle of the humanities and the social sciences is to achieve a form of understanding instead of an explanatory framework of causation; understanding in anthropological and sociological terms still makes certain commitments to true phenomena. For instance, to understand and describe social norms entails a certain truth about social norms. This is further amplified in the political and ethical arena where certain values and the arguments that underpin them are held to be true. This is easily demonstrated by the fact that most societies advance the idea that civil equality is just and it is true that it is just or that it is true that murder and rape is wrong.
As noted there are several different theories of truth. There are the realist theories which argue that truth is a universal concept that is solely external to the mind and is empirically verifiable, the anti-realist positions which argue that any position of truth is constantly in flux and theory dependent, the pragmatist's position on truth which conjoins aspects of external verification with the psychological phenomena of theory construction; and the pluralistic theory of truth which argues that truth's universality is its function but that in distinct domains there are differences regarding the constitution of truth. These are all tenable arguments regarding the nature of truth, its validity, its applicability and its employment; and they all have both forceful and detrimental attributes. They can be individually argued in isolation but all of them appear to suffer one common problem and that is their eventual use in meta-pictures of reality and existence.
This ultimate problem is encountered when one considers coherence theories of truth. Regardless of which of the above approaches to truth you endorse, any idea, justification and eventual explanation about fundamental reality and existence itself is arguably bound up with the coherence theory of truth. A coherence theory of truth states that the truth of any (true) proposition consists in its coherence with some specified set of propositions. When applied to absolute truth this can give rise to competing world views from individuals who occupy the same time and space and are aware of the same facts, propositions and statements. For example two scientists can be realists and adhere to the correspondence theory of truth, accepting the same truth about factual elements in any scientific discipline but in terms of absolute reality and existence one may be an atheist and the other a theist. Subsequently they agree on a correspondence theory of truth but differ when it comes to a coherence view of truth regarding meta-truths about absolute reality and existence as a consequence of how several independent facts themselves cohere. With this is mind the lasting problem regarding the concept of truth in philosophy is not necessarily an array of competing theories of truth but how one then applies a single theory of truth to meta-pictures of absolute reality. Irrespective of the position one takes on truth in a singular way, one seems to end up at the problematic avenue that is the final coherence theory of truth.