Understanding Underdetermination in conjunction with realism and instrumentalism
The present essay is about the understanding of under determination thesis in conjunction with the realism and instrumentalism. As we know that realism and instrumentalism are two opposite views in philosophy of science, so by explaining both it might be much simpler to grasp the idea of under determination thesis, which is one of complex doctrine.
The intended audiences of the essay are science student's and people who are interested to know about the philosophical issues in science. I divide the essay into four of parts. The first part explains the realism and instrumentalism concepts, second part explains the under determination thesis at length and then the third part will state the views of different philosophers about three schools of thoughts. The fourth and the ultimate part conclude the complete argumentation
The word realism in the dictionary means the tendency to see or represent things as they really are. [dic]. In philosophy of science it could be defined as "the philosophical doctrine that abstract concepts exist independent of these names". It could be explained as an approach in philosophy that considers objects because they are in the universe as real things and their characteristics as a second thing. The advocate of realism are called realist and it is important to differentiate the realist's.
A person can be realist about the several kinds of things i. e. mountains, physical objects, numbers, universe etc. but in the case of a philosopher, it must specify that for what object/thing the philosopher is realist [book]. An American philosopher name Hilary Putnam stated that "A realist with respect to a given theory holds the next:
What makes them true or false is something external that is to say, it is not generally our sense data, actual or potential, or the structure in our minds, or our language, etc.
Furthermore he says that the positive argument for realism is that it's really the only "philosophy that will not make the success of science a miracle". [Book]. Generally, in science established scientific theories are treated as a true fact, but according to realist these theories would be treated as an effective explanation of the whole scientific process or its relation to an object, and not all together truth. [Book] An example is that sun, mountains, building etc. exists nowadays, but the attributes like length, width, colour etc. are either dependent or in addition to the environment.
For example sunlight is spherical in shape, so it is independent from any material thing of the universe. However in case of any building, its shape and size, all depend upon the person who designed or built it. So that it can be said that the truth is related to mind and environment.
In general, Realism is supposed to be always a term that pertains to range of subjects i. e. ethics, aesthetics, causation, modality, science, mathematics, semantics etc. When we discuss the realism in the context of science then the intention is to elaborate the scientific realism that includes a amount of dimensions i. e. metaphysical, epistemological and methodological. Besides this it is also the fact there is no single version of scientific realism which is being accepted by all the scientific realists.
The doctrine of scientific realism states that " the globe studied by science exists and has the properties it can, independently of our own beliefs, perceptions, and theorizing; that the aim of science is to spell it out and describe that world, including those many aspects of it that aren't directly observable; that, other activities being equal, scientific theories should be interpreted literally; that to simply accept a theory is to assume that what it says about the planet is true, and this by continually replacing current scientific theories with better ones. Science makes objective progress and its theories get nearer to the truth".
Realism has two schools of thought, first one is called Extreme realism, represented by William, a French philosopher; according to him "universals exist independently of both the human mind and particular things". The second the first is moderate realism and according to which "universals exist only in the mind of God, as patterns where He creates particular things". The primary proponent of this view was St. Thomas Aquinas and John of Salisbury.
According to epistemological view of realism, things exist in this universe, independent in our understanding or perception. This aspect is very opposite to the idea of idealism, which states that "reality exists only in your brain".
By having a brief explanation of realism, instrumentalism will be discussed, which is the opposite view of realism and the majority of time called Antirealism. Antirealism is a doctrine that rejects realism, and includes instrumentalism, conventionalism, logical positivism, logical empiricism and constructive empiricism.
Instrumentalism is treated as a doctrine that states "theories are simply just instruments, tools for the prediction and convenient summary of data" [Book]. Quite simply it can be defined as "concepts and theories are merely useful instruments whose worth is measured not by whether the concepts and theories are true or false, but by how effective they are really in explaining and predicting phenomena".
The point is the fact that in order to make predictions from theories, logic is necessary, so that it can be hard to say theories have no truth values. Because of this instrumentalists admit that theories have truth values, but do not accept this argument that theories should be treated as accurately true. Because of this T. S. Kuhn said that "Theories may have truth values but their truth of falsity is irrelevant to your knowledge of science". [Book]
In other words instrumentalism evaluates the significance of a theory regarding empirical evidence and didn't require the understanding of the actual phenomena. For example Newton gravity model is understandable and working fine, but it does not have any theoretical foundation [Answer. com]
The another aspect of instrumentalism is the fact it relates closely to pragmatism which point of view opposes the scientific realism because according to this, theories are pretty much true in nature. Moreover, instrumentalism refutes that theories can be evaluated on the basis of truth. Theories will never be regarded as air plane black box which gives output based on observed input. The main point is that there should be a specific distinction between theory and observation that further brings about a distinction between terms and statements in each kind.
Like in science for statement of observation there's a specific meaning for an observable truth, for example if "the litmus paper is red", therefore the observation terms have their meaning fixed by their discussing observable things or properties, e. g. "red". Theoretical statements have their meaning fixed by their function within a theory and aren't truth evaluable, e. g. "the answer is acidic", whereas theoretical conditions have their meaning fixed by their systematic function within the theory and do not make reference to any observable thing or property, e. g. "acidic".
Though you might think that "acidic" refers to a genuine property in an object, this is of the word can only just be explained by reference to a theory about acidity, as opposed to "red", which really is a property you can observe. Statements that mix both T-terms and O-terms are therefore T-statements, since their totality can't be directly observed".
There is some criticism of this distinction, however, as it confuses "non-theoretical" with "observable", and likewise "theoretical" with "non-observable". For example, the word "gene" is theoretical (so a T-term) but it may also be observed (so an O-term). Whether a term is theoretical or not is a semantic matter, since it involves different ways that the word gets its meaning (from a theory or from an observation).
Whether a term is observable or not can be an epistemic matter, because it involves how we can come to learn about it. Instrumentalists contend that the distinctions are the same, that we can only just come to know about something if we can understand its meaning according to truth-evaluable observations. So in the above mentioned example, "gene" is a T-term because, though it is observable, we can not understand its meaning from observation alone.
The explanation of realism and instrumentalism above has provided us the ability to understand the topic with much insight. Now, I switch to under determination thesis. From the above discussion we've the data that instrumentalism is related to pragmatism which viewpoint is contrasts with the scientific realism, which states that theories are often pretty much true. Here, I make reference to Quine, who said that theories can be underdetermined by all possible observations , and Newton Smith's, regard this as a threat to realism. He said, realism in his sense should be rejected if there may be cases of under determination of theories.
As we know that under determination is a thesis that is "found in the discussion of theories and their regards to the data that is cited to support them".  Arguments from under determination are being used to aid epistemic relativism by claiming that there is no good way to certify a theory predicated on any set of evidence. A theory is underdetermined if, given the available evidence, there's a rival theory which is inconsistent with the idea that is at least as consistent with the data. Moreover, under determination is treated an epistemological issue about the relation of evidence to conclusions.
The subject gets its first attention by Ren Descartes, a French philosopher and mathematician in the 17th century. He presented two arguments related to under determination.
"While dreaming, perceived encounters (for example, falling) do not necessarily contain sufficient information to deduce the true situation (being in bed)".  As we realize that it's not always possible for a person to split up dreams from reality and the theory that what is real or dream at a certain time is underdetermined.
The second argument of Descartes's is named demon argument "which is a variant of the dream argument that posits that of one's experience and thoughts might be manipulated by a very powerful being (an "evil demon") that always deceives. Once again, so long as the perceived reality appears internally consistent to the limits of one's limited ability to share with, the situation is indistinguishable from reality, one cannot logically determine between correct beliefs from being misled; this is another version of under determination". 
The second person who talks about under determination was David Hume, would you not use the word under determination specifically but a disagreement about the condition of induction. I'll discuss the induction later in the essay while explaining the under determination types.
The Under determination thesis gets the recognition in the twentieth century through the work of Thomas S. Kuhn, who is a famous theoretical physicist and philosopher. He was very much prominent due to his work, The Structure of Scientific Revolutions that offered an alternative solution to linear types of scientific progress. According to Kuhn the under determination has a spot to for argumentation against theories in the philosophy of science, and scientific realism. According to Khun the under determination can be divided into two types the weak and strong under determination. The both could be mentioned in the next words:
Weak underdetermined is that the available evidence is not sufficient to prove the argument, but some evidence that will be available in the foreseeable future might do this.
Strong underdetermined is to claim that it is especially impossible to get evidence which could fully resolve the argument between your opponent theories.
Besides strong and weak underdetermined theory there are two other attributes called deductive and inductive under determination. Both rival theories could be deductively underdetermined when the available evidence will not completely deny either theory. The theory is inductively underdetermined when theories are appropriate for the available evidence, but nonetheless tries to determine, which theory could be an improved failure
A weak under determination can change to a strong one if it avoids the attainment of future evidence that turns it into deductive under determination. A counter argument is that it is not possible for a theory to be accurately strong and inductive.
In general weak under determination arguments are centered on the availability of evidence for an explicit set of theories, and strong under determination mostly entails common epistemological arguments that relates to the kind of evidence and its viability for a specific or general theory. Furthermore, it is normally acknowledged that all theories are weakly underdetermined, however in case of some specific purpose all theories are strongly underdetermined.
Explaining the types of under determination thesis, Ludan said that "for just about any finite body of evidence, there are indefinitely many mutually contrary theories, each which logically entails the evidence". So in other words it could be said that deductive under determination is under determination of selecting theory via a logical method.
Finally, the word under determination as thesis is associated with two respectable names Pierre Duhem and W. V. Quine in philosophy of science, "that neither the reality nor the falsity of any scientific theory is determined by evidence".
According to Duhem-Quine Under determination is a "relation between evidence and theory. More accurately, this is a relation between your propositions that express the (relevant) evidence and the propositions that constitute the idea. Evidence is said to underdetermine theory".
From the aforementioned it could be said that evidence is insufficient to prove the theory, belief or truth. Moreover, only the option of evidence is insufficient to help make the theory a credible one. Because of this we can call the first argument a deductive and the next inductive under determination. Hence, according to under determination thesis, both arguments have required some definite epistemic proposition, and belief in a theory could not be justified on the basis of evidence. At under determination types, Duhem, also said that "logic alone cannot take us from the falsification of the prediction to a refutation of the isolated hypothesis. Importantly, deductive under determination does not imply that theory choice is underdetermined, nor will it really mean that there may be more than one reasonable conclusion given certain experimental evidence".
Up until now we have a basic knowledge of the under determination thesis, so now I will discuss what realism happens to be, the theoretical frame and the origin of the idea.
Another argument against scientific realism, deriving from the under determination problem, is not as historically motivated as these others. It claims that observational data can in principle be explained by multiple theories that are mutually incompatible. Realists counter by pointing out that there were few actual cases of under determination in the annals of science. Usually the necessity of explaining the info is so exacting that scientists are lucky to find even one theory that fulfils it.
Furthermore, if we take the under determination argument seriously, it means that we can know about only what we've directly observed. For instance, we could not theorize that dinosaurs once lived predicated on the fossil evidence because other theories (e. g. , that the fossils are clever hoaxes) can take into account the same data. Realists claim that, in addition to empirical adequacy, there are other standards for theory choice, such as parsimony.
In particular, it must not be confused using what Newton-Smith takes to be a "minimal common factor among the wide range of philosophers who in recent years have advocated a realist construal of scientific theories". This common factor involves the following theses:
(1) "Scientific theories are either true or false and which a given theory is, it is at virtue of the way the world is",
(2) "If a theory holds true, the theoretical conditions of the theory denote theoretical entities that are causally responsible for the observable phenomenon whose occurrence is evidence for the theory",
(3) "We are able to have warranted beliefs (at least in principle) regarding the truth values of theories",
(4) "The historically produced sequence of theories of an adult science may well be a sequence of false theories but it is just a sequence in which succeeding theories have greater truth-content and less falsity content than their predecessors". We might make reference to (1) as the objectivity, (2) as the causality, (3) as the decidability, and (4) as the convergence of scientific theories.
Newton-Smith uses the name "realism" for the combo of these four theses, and he also seems to hold that this is the typical use of the word. It is clear that theoretical realism in the weakest sense entails neither objectivity, nor causality, nor decidability, nor convergence. Specifically, some theoretical propositions may be true even if no scientific theory as a whole is either true or false.
Moreover, it is doubtful whether realism in Newton-Smith's sense entails theoretical realism. For instance, if all theoretical propositions are false, then theoretical realism is false, but realism in Newton-Smith's sense might be true. Regardless, one of Newton-Smith's main theses is that realism in his sense needs to be rejected if there may be cases of under determination. In particular, he claims that either objectivity or decidability needs to be weakened if under determination may appear to give up decidability is what he calls the ignorance response (to under determination).
This "involves embracing the opportunity of inaccessible facts - facts concerning whose obtaining we could haven't any information". To give up objectivity is exactly what he calls the arrogance response. This "amounts to holding that if we cannot know about something you can find nothing to learn about". 36 Notice, that this holds only for under determination in Newton-Smith's sense, i. e. under determination by all possible data.
It does not hold for the other kinds of under determination mentioned above. In other words, it is only when an underdetermined theory is empirically viable that people cannot know that it's true or that it is false (either because it is neither true nor false, or because we cannot know, even in principle, what its truth value is). Generally, we can not have under determination (of any sort) together with empirical viability, objectivity, and decidability. When a theory is underdetermined, we cannot know that it is true. This I accept.
At first, it appears that Quine would not accept this. He holds that there could be two best total theories that happen to be empirically viable and incompatible, but that we may know, at least in principle, that one of these is true and the other false. However, it appears that Quine is then using "true" and "false" in a non-realistic sense; according to him, "to call a statement true is merely to reaffirm it". He will not seem to be to assume that there is some objective reality, "the globe", such that the truth of any statement consists it its correspondence with this reality. Hence, presumably he would reject the objectivity thesis which is part of realism in Newton Smith's sense.
Given the many epistemological difficulties (under determination, problem of induction, rationality, social forces), and the lack of a consensus on these issues, why should we feel that our theories are actually describing reality?
The apparently large gap between observational and theoretical knowledge inspires worry about realism
Metaphysical difficulties enter into play here as well-we do not have good understandings of the type of laws and causation, explanation, just how can we claim that we are discovering the type of the universe?