In the most general sense, realism is the view that there are entities in this world that exist that are mind-independent. In essence, scientific realism offers a certain portrayal of what a scientific theory is and what constitutes its acceptance based on truth. A scientific realist holds 2 fundamental principles: science aims to give us a literally true account of what the world is like through theories, and that accepting a scientific theory involves the belief that it is true.
In stark contrast to this view, constructive empiricism, or rather scientific anti-realism, holds that acceptance of a scientific theory involves only the belief that the theory is empirically adequate, thus differing from the scientific realist view, however it does hold that the aim of science does provide true descriptions of only a certain part of the world, that is, the observable part.
Moreover, constructive empiricism then raises a heavily disputed argument of underdetermination – the thesis explaining there always exists a rival theory to our own scientifically based theories, which is supported by the evidence, and that this theory can be logically maintained even in the case of confronting new evidence. The notions of data equivalence and empirical equivalence become the pivotal points of argument and exploration throughout this essay.
I attempt to defend the ‘optimistic’ scientific realist by exploring different forms of underdetermination, and the current impotency of underdetermination in disturbing the scientific realist view as a result of our seemingly endless, yet limited, natural knowledge. It is important to note that the scientific realist does not simply assert that science seeks the truth of the world, but rather it has a fundamentally epistemological rationale that is often overlooked and will be further defined throughout this essay.
From a scientific realist’s perspective, the scientific pursuit of truth further gives rise to genuine knowledge of the natural world, thus entailing epistemic realism and accordingly yielding the knowledge of truth about the objective reality investigated by scientists (Sankey, 2008). Epistemic realism characterises scientific realism, insisting that scientific knowledge is not restricted to the observational level, but also unobservable aspects of reality as well. On the contrary, contemporary versions of constructive empiricist deny the possibility of having rationally justified belief or knowledge about unobservable aspects f the world (Sankey, 2008).
Accordingly, within substructures of theory’s models, the establishment of observable phenomena corresponds to the empirical adequacy of a theory. As such, anti-realist’s account of empirical adequacy rests heavily on the question of what is observable and unobservable. As Bas C. Van Fraassen, a distinguished Professor of Philosophy and renowned anti-realist illustrates the concept, if circumstances are present such that X is present to us under those circumstances, then we can observe X (Van Fraassen, 1980).
It is important to note that an individual only observes something when the observation is unaided, for example, cells are not seen through a microscope, but rather an image is seen by which both realists and anti-realists see differently (Monton & Mohler, 2014). In light of this notion, observability is relativised to the members of the epistemic community, which are the subject of scientific theory. Moreover, the constructive empiricist takes what counts as observable as the subject of scientific theory rather than something that can be deduced by a priori, for example, a tautology or ontological proof.
It is then safe to say that science itself is the arbiter of what counts as observable, and that the constructivist view denies the epistemic access to the mind-independent world, which lies beyond our human-sense experience. Thus far, a potential threat to scientific realism is that theories may be shown to be ‘underdetermined by the evidence’ in a seemingly specific sense. Suppose an empirically successful accepted theory T, and its rival T’, which is equally empirically successful, but makes claims that are quite different from those of T about the ‘deep structure’ of the universe (Worrall, 2011).
As such, the theories make all the same predictions about what’s observable, but differ in regards to what is unobservable. In light of the evidence, the realist must then consider both theories as equally good, and thus by supposition, they are rivals and both cannot be considered to be true. However, in the case of the constructive empiricist, empirical adequacy is the only rational candidate for the belief involved in a theory’s acceptance and as such underdetermination does not effect their position.
Consider the two most prominent theories in contemporary physics: the general theory of relativity and the quantum theory. These two theories are considered not absolutely inconsistent yet they are mutually incompatible (Worrall, 2011). The quantum theory states that everything is quantised, while the general theory does not consider space-time to be quantised. The general theory states that all laws are covariant, but the quantum theory is not a covariant theory. So which is seen to be true from the perspective of the scientific realist?
This example illustrates the threat that underdetermination poses in disintegrating the argument for scientific realism. However, on the counteractive side, a scientific ‘optimistic’ realist advances their rationale by placing belief in the ‘approximate truth’ of the theories rather than absolute belief in the truth (Worrall, 2011). The pessimistic meta-induction argument forms the basis underlining theory change throughout history, providing a list of predictively successful and accepted theories that have previously been replaced by theories inconsistent with them.
In light of this notion, there is no possible argument that can maintain that the currently accepted theories will withstand replacement in the future by theories that are inconsistent with them (Worrall, 2011). As such, the only plausible argument is that currently accepted theories are likely to prove an approximate truth, just as rejected theories had counted as approximate truth from the perspective of the current theories. Essentially, two mutually incompatible theories cannot both be true, but they may both be approximately true, that is, both may progress to the limiting cases by which a superior theory emerges.
This can be seen in Newton’s attitude toward Copernican theory, in which nothing in Newton’s modified version of the ‘third motion’ of the Earth corresponded to that of Copernicus’. In a more current example, the general theory of relativity and the quantum theory follows this notion, in which physicists expect these theories to emerge as limiting cases. In essence, anyone can be a realist about a theory without even expecting that all of it will be preserved in future theories. Thus far, the threat to realism from underdetermination becomes more difficult to condition.