Why one theory replaces another

It has been claimed by Psillos that the foregoing objection is misguided. The problem is this. There are the theories scientists currently endorse and there are the theories that had been endorsed in the past. Some but not all of them were empirically successful perhaps for long periods of time. They were empirically successful irrespective of the fact that, subsequently, they came to be replaced by others.

This replacement was a contingent matter that had to do with the fact that the world did not fully co-operate with the then extant theories: some of their predictions failed; or the theories became overly ad hoc or complicated in their attempt to accommodate anomalies, or what have you. The replacement of theories by others does not cancel out the fact that the replaced theories were empirically successful.

Even if scientists had somehow failed to come up with new theories, the old theories would not have ceased to be successful. So success is one thing, replacement is another. Hence, it is one thing to inquire into what features of some past theories accounted for their success and quite another to ask whether these features were such that they were retained in subsequent theories of the same domain. These are two independent issues and they can be dealt with both conceptually and historically independently.

One should start with some past theories and—bracketing the question of their replacement—try to identify, on independent grounds, the sources of their empirical success; that is, to identify those theoretical constituents of the theories that fuelled their successes.

When a past theory has been, as it were, anatomised, we can then ask the independent question of whether there is any sense in which the sources of success of a past theory that the anatomy has identified are present in our current theories. A refinement of the divide et impera move against the PI has been suggested by Peter Vickers He argues that the onus of proof lies with the antirealist: the antirealist has to reconstruct the derivation of a prediction, identify the assumptions that merit realist commitments and then show that at least one of them is not truthlike by our current lights.

But then, Vickers adds, all the realists need to show is that the specific assumptions identified by the anti-realist do not merit realist commitments. It should be noted that this is exactly the strategy recommended by Psillos in his , where he aimed to show, using specific cases, that various assumptions such as that heat is a material substance in the case of the caloric theory of heat, do not merit realist commitment, because there are weaker assumptions that fuel the derivation of successful predictions.

Vickers generalizes this strategy by arguing as follows. Take a hypothesis H that is taken to be employed in the derivation of P and does not merit realist commitment. An instance of the divide et impera strategy is structural realism. This view has been associated with John Worrall , who revived the relationist account of theory-change that emerged in the beginning of the twentieth century.

In opposition to scientific realism, structural realism restricts the cognitive content of scientific theories to their mathematical structure together with their empirical consequences. But, in opposition to instrumentalism, structural realism suggests that the mathematical structure of a theory represents the structure of the world real relations between things.

Against PI, structural realism contends that there is continuity in theory-change, but this continuity is again at the level of mathematical structure. Structural realism was independently developed in the s by Grover Maxwell a, b in an attempt to show that the Ramsey-sentence approach to theories need not lead to instrumentalism.

Ramsey-sentences go back to a seminal idea by Frank Ramsey The key idea here was that a Ramsey-sentence satisfies both conditions i and ii.

A key problem with Ramsey-sentence realism is that though a Ramsey-sentence of a theory may be empirically inadequate, and hence false, if it is empirically adequate if, that is, the structure of observable phenomena is embedded in one of its models , then it is bound to be true.

More recently, David Papineau has argued that if we identify the theory with its Ramsey-sentence, it can be argued that past theories are approximately true if there are entities which satisfy, or nearly satisfy, their Ramsey-sentences.

The advantage of this move, according to Papineau, is that the issue of referential failure is bypassed when assessing theories for approximate truth, since the Ramsey sentence replaces the theoretical terms with existentially bound variables.

But as Papineau admits, the force of the historical challenge to realism is not thereby thwarted. For it may well be the case that the Ramsey-sentences of most past theories are not satisfied not even nearly so. In the more recent literature, there has been considerable debate as to how exactly we should understand PI. PI can … be described as a two-step worry. First, there is an assertion to the effect that the history of science contains an impressive graveyard of theories that were previously believed [to be true], but subsequently judged to be false … Second, there is an induction on the basis of this assertion, whose conclusion is that current theories are likely future occupants of the same graveyard.

Yet, it is plausible to think that qua an inductive argument, history-based pessimism is bound to fail. The key point here is that the sampling of theories which constitute the inductive evidence is neither random nor otherwise representative of theories in general. It has been argued that, seen as an inductive argument, PI is fallacious: it commits the base-rate fallacy cf. Lewis If in the past there have been many more false theories than true ones, if, in other words, truth has been rare , it cannot be concluded that there is no connection between success and truth.

Take S to stand for Success and not- S to stand for failure. Analogously, take T to stand for truth of theory T and not- T for falsity of theory T. Assume that is, that there is a very high True Positives successful but true rate and a small False Positives successful but false theories rate. We may then ask the question: How likely is it that a theory is true, given that it is successful? But this does not imply something about the connection between success and truth.

It is still the case that the false positives are low and that the true positives high. The low probability is due to the fact that truth is rare or that falsity is much more frequent. Similarly, the probability that a theory is false given that it is successful i. As Peter Lewis put it:. At a given time in the past, it may well be that false theories vastly outnumber true theories. In that case, even if only a small proportion of false theories are successful, and even if a large proportion of true theories are successful, the successful false theories may outnumber the successful true theories.

So the fact that successful false theories outnumber successful true theories at some time does nothing to undermine the reliability of success as a test for truth at that time, let alone at other times —7. Seen in this light, PI does not discredit the reliability of success as a test for truth of a theory; it merely points to the fact that truth is scarce among past theories.

Challenging the inductive credentials of PI has acquired a life of its own. A standard objection cf. That is, theories are diverse enough over time, structure and content not to allow us to take a few of them—not picked randomly—as representative of all and to project the characteristics shared by those picked to all theories in general.

In particular, the list that Laudan produced is not a random sample of theories. They are all before the twentieth century and all have been chosen solely on the basis that they had had some successes irrespective of how robust these successes were. An argument of the form:. Things would be different, if we had a random sampling of theories. These 40 were then divided into three groups: accepted theories, abandoned theories and debated theories.

Mizrahi then notes that these randomly selected data cannot justify an inductively drawn conclusion that most successful theories are false. On the contrary, an optimistic induction would be more warranted:. Mizrahi has come back to the issue of random sampling and has attempted to show that the empirical evidence is against PI:.

If the history of science were a graveyard of dead theories and abandoned posits, then random samples of scientific theories and theoretical posits would contain significantly more dead theories and abandoned posits than live theories and accepted posits. It is not the case that random samples of scientific theories and theoretical posits contain significantly more dead theories and abandoned posits than live theories and accepted posits.

Therefore, It is not the case that the history of science is a graveyard of dead theories and abandoned posits. A similar argument has been defended by Park This has been adopted by Michael Devitt too, though restricted to entities. In a similar fashion but focusing on current theories, Doppelt claims that realists should confine their commitment to the approximate truth of current best theories, where best theories are those that are both most successful and well established.

The asymmetry between current best theories and past ones is such that the success of current theories is of a different kind than the success of past theories. The difference, Doppelt assumes, is so big that the success of current theories can only be explained by assuming that they are approximately true, whereas the explanation of the success of past theories does not require this commitment.

If this is right, there is sufficient qualitative distance between past theories and current best ones to block. Doppelt This singular degree of empirical confirmation amounts to raising the standards of empirical success to a level unreachable by past theories cf.

Hence, the standards of empirical success change slower than theories. Hence, it is not very likely that current standards of empirical success will change any time soon. It has been argued, however, that Doppelt cannot explain the novel predictive success of past theories without arguing that they had truthlike constituents cf. Alai The key point of this strategy is that the history of science does not offer a representative sample of the totality of theories that should be used to feed the historical pessimism of PI.

In order to substantiate this, Fahrbach suggested, based on extensive bibliometric data, that over the last three centuries the number of papers published by scientists as well as the number of scientists themselves have grown exponentially , with a doubling rate of 15—20 years.

As such the sample is totally unrepresentative of theories in total; and hence the pessimistic conclusion, viz. Moreover, Fahrbach argues, the vast majority of theories enunciated in the last 50—80 years, which constitute the vast majority of scientific work ever produced are still with us.

Hence, as he puts it,. Every scientific theory starts as a hypothesis. A scientific hypothesis is a suggested solution for an unexplained occurrence that doesn't fit into a currently accepted scientific theory. In other words, according to the Merriam-Webster Dictionary , a hypothesis is an idea that hasn't been proven yet. If enough evidence accumulates to support a hypothesis , it moves to the next step — known as a theory — in the scientific method and becomes accepted as a valid explanation of a phenomenon.

Tanner further explained that a scientific theory is the framework for observations and facts. Theories may change, or the way that they are interpreted may change, but the facts themselves don't change.

Tanner likens theories to a basket in which scientists keep facts and observations that they find. Some may not be satisfied with the methods adopted to test the propositions; others simply may not believe the theory explains or defines reality and propose alternative theories. In the social sciences it is even more complicated than the physical sciences.

The interpretations of outcomes and behaviours are subject to individual research interpretations and the full range of factors impacting on the economy, for example, are much more difficult to control or isolate. Does the reintroduction of a theory mean that it should not have been replaced in the first place?

Theories about how the economy works and what will happen in the economy where there is monetary policy or fiscal policy intervention are appropriate in assisting policymakers understand the possible implications of decisions they make or are under consideration. However, they are rarely complete models and often outcomes cannot be predicted. Reintroduction of a theory suggests that new evidence in support of the theory has been reported.

Should a theory be discarded if it does not specify the means of achieving a stated objective? Explain your answer. The application of the theory can have many elements and it is in the interpretation of what will induce the predicted effects in the economy predicted by the theory which will result in predicted or other stated outcomes.

Instructors should ask the students to discuss how we would know whether a reduction of corporate interest rates resulted in an increase in the inflation rate? Given this definition, who is ultimately responsible for the rogue trading outlined in the Societe Generale scandal: the trader directly involved; management, who are responsible for the high-risk, high-reward framework in which the trader operated; or a combination of both?

Obviously all parties are responsible for their actions. Classical mechanics In the s, building on the ideas of others, Isaac Newton constructed a theory sometimes called classical mechanics or Newtonian mechanics that, with a simple set of mathematical equations, could explain the movement of objects both in space and on Earth.

This single explanation helped us understand both how a thrown baseball travels and how the planets orbit the sun. The theory was powerful, useful, and has proven itself time and time again in studies; yet it wasn't perfect …. Science at multiple levels Summing up the process. How science works page 20 of 21 previous next. Accepted theories are the best explanations available so far for how the world works.

They have been thoroughly tested , are supported by multiple lines of evidence , and have proved useful in generating explanations and opening up new areas for research. However, science is always a work in progress, and even theories change. We'll look at some over-arching theories in physics as examples: Classical mechanics In the s, building on the ideas of others, Isaac Newton constructed a theory sometimes called classical mechanics or Newtonian mechanics that, with a simple set of mathematical equations, could explain the movement of objects both in space and on Earth.