Summary of Philosophy of Science: A Very Short Introduction by Okasha - 2nd edition

Science wants to explain the world around us, partly for practical ends, and partly to satisfy our curiosity. But what is scientific explanation? Our starting point to look at this question will be Carl Hempel who thought about this in the 1950s.

What is Hempel's covering law model of explanation?

Hempel figured that scientific explanations are usually given in response to "explanation-seeking why-questions", so questions that demand explanation. A scientific explanation provides an answer, and to know what a scientific explanation is, he thought, the essential features of such an answer should be determined.

He said scientific explanations usually have the logical structure of an argument: a set of premises, followed by a conclusion. The conclusion states that the phenomenon that needs explaining occurs and the premises then tell us why this is true. So the premises should explain the conclusion. Hempel's answer to this problem contained three things. First, the premises should entail the conclusion: thus, deduction. Second, the premises should all be true. And third, they should consist of at least one general law, sometimes also called laws of nature. 

The phenomenon to be explained is named the explanandum and the general laws and particular facts that explain it are the explanans. The explanandum may be either specific or general. 

So, this model says that the essence of explanation is to show that the phenomenon is "covered" by a certain law of nature. But not all scientific explanations fit this model. Hempel knew this, but said that if the explanation were spelled out completely and very detailed, there would still be some law of nature. Furthermore, Hempel said that every scientific explanation can also be a prediction. If the phenomenon was not yet known, it could have predicted it. And then also reliable prediction is also a possible explanation. So explanation and prediction are structurally symmetric. However, in some cases this definitely does not work, not everything that can be predicted can also be explained in the same way later.

Still, there are cases that fit Hempel's model but are not really scientific explanations. Two cases are:

• The problem of symmetry. Explanation is an asymmetric relation: that x explains y does not mean that y explains x in the same way. Hempel's model does not respect this asymmetric relation and therefore includes things that are not really scientific explanations. 

• The problem of irrelevance. A good explanation should contain the relevant information. "Explanations" that actually use the irrelevant information and can not be viewed as good explanations, but still have a correct  structure of explaining, can be included in Hempel's model which is not good.

What does causality mean in explanation?

When looking for a better model, some believe the key lies in the concept of causality: because often, what causes something is what explains it. In some of the problems with the covering law model, the causal models do succeed. It could also be that because causality is obviously asymmetrical, explanations are asymmetric too. 

Hempel was an empiricist, and empiricists are often suspicious of the causality concept. Empiricism states that all knowledge comes from experience. Like Hume, who thought: it's impossible to experience causal relations, so they don't actually exist; it's what we, humans, make of it. Empiricists treated causality with much caution, which is why Hempel did not take it into account. In recent years, empiricism has decreased in popularity.

Still, also causality-based accounts encounter less fitting cases. For example, theoretical identifications, like: water is H2O or temperature is molecular kinetic energy. These terms explain what these concepts are, but it has nothing to do with causality.

Can science explain everything?

There's many things science has explained, and there's many things left to uncover, probably possible due to always evolving science. However, some philosophers think science will never explain everything, because in order to explain something, something else needs to be invoked - and what explains the second thing then? Fundamental laws have to be used and probably at least some will themselves remain unexplained. Some philosophers think for example consciousness, and its subjective aspect, can never be fully explained. But it seems that only time can really tell.

What is multiple realization?

Most people think of physics as the most fundamental science, since all of the other sciences also study things that are made up of physical particles. Still, the other sciences seem largely autonomous and also important. But why can the other sciences not be reducible to physics? Some philosophers say that's because the objects studied by the higher-level sciences are multiply realized at the physical level. There is no limit on the range of different physical properties that a lot of things can have, because they are multiply realized at the physical level. For example, you can not say: "x is an ashtray if and only if x is...." as there are so many possibilities. The vocabulary of fundamental physics is not elusive enough for this.

What was the logical empiricist philosophy of science?

The dominant post-war philosophical movement was logical empiricism. Hempel and Popper were part of this movement. It started in the 1920s and went on until the mid-1960s. They had a high regard for the natural sciences and maths and all the exciting scientific advances, they even wanted to make philosophy more scientific. They loved the apparent objectivity in science, and viewed it as a rational activity. They paid little attention to the history of scientific ideas, because they drew a distinction between the "context of discovery" and the "context of justification". The context of discovery meant the actual historical process, by which a scientist arrives at a theory, and the context of justification is the means by which the scientist tries to justify a theory once they have it. The logical empiricists viewed the context of discovery as subjective and the context of justification as objective, and so they focused on the latter. Another theme in logical empiricism was the distinction between theories and observational facts. They believed disagreements between theories could be solved by comparing the theories with the neutral observational facts. 

What was Kuhn's theory of scientific revolution?

Kuhn was a philosopher that also focused on the philosophy around scientific change. He thought that the fact that too little attention was paid to the history of science had led the logical empiricists to have an inaccurate view of science. He was very interested in scientific revolutions, where there was a fundamental change in scientific worldview. When there was no scientific revolution at that time, he would call it "normal science". Central to his idea of normal science is the concept of a paradigm. A paradigm consists of two main components: namely a set of fundamental theoretical assumptions which all members of a scientific community accept, and a set of exemplars, or particular scientific problems, which have been solved using those theoretical assumptions, and which appear in the textbooks of the discipline. A paradigm is basically an entire scientific outlook, which unites a scientific community, and allows normal science to happen.

Normal science is, according to Kuhn, basically puzzle-solving. A paradigm will encounter problems, and a scientist should "solve" these problems, while making as few changes to the paradigm as possible. So, normal science is conservative. Normal scientists do not want to test the paradigm, says Kuhn.

A period of normal science can last very long, but over time anomalies are discovered (problems to the paradigm that can not be fixed). As these anomalies accumulate, there is some sort of crisis in the scientific community, where confidence in the paradigm decreases. Then, a period of revolutionary science comes through, and there is a search for a new paradigm. When all members of the scientific community are won over to the new paradigm, the scientific revolution is completed, and this can take quite a while. 

Kuhn also advanced some controversial philosophical theses. He said that adopting a new paradigm also involves some kind of faith on the part of the scientist. Just reasoning or evidence is not enough, as faith is also necessary. He also talked about the peer pressure of scientists on one another, when discussing how paradigms gain acceptance in the scientific community. A lot of people were shocked by this, because Kuhn included these subjective elements of faith and peer pressure, making science not as rational as many wanted it to be. 

Kuhn was also controversial in discussing the overall direction of scientific change. The dominant view was that science progresses towards the truth in a linear fashion. Newer, correcter ideas replace older, less accurate ones. Kuhn disagreed with this. And Kuhn also doubted if the term objective truth even makes sense: he doubted that there was a fixed set of facts about the world, independent of paradigms. He thought facts about the world are paradigm-relative. He was very anti-realistic. 

What is incommensurability and the theory-ladenness of data?

For these claims, Kuhn had two main philosophical arguments. Firstly, he said that competing paradigms are "incommensurable" with another. This means that the paradigms are so different, there is no comparison possible, and there is no common language in which both can be translated. So, before and after a paradigm shift, according to Kuhn scientists "live in different worlds". Kuhn was very holistic. He thought that scientific concepts get their meaning from the theory in which they play a part. So for example to understand Newton's concept of mass, you need to understand the whole Newtonian theory. This is because mass can mean different things in different theories, Kuhn said. 

Kuhn used his idea of incommensurability to discredit the view that paradigm shifts are completely objective, and also to support his non-cumulative view of the history of science. He thought, since you can not compare two viewpoints as they are basically in different languages, subjectivity is always included. And if old and new paradigms are incommensurable, there is not a linear development of science possible. Later is not always better, as it's completely different and not comparable.

Kuhn did not convince many other philosophers with this theory. Part of the problem was that Kuhn also said old and new paradigms are incompatible, which makes sense because if they were compatible, there would be no need to choose. But, if two things are incommensurable, then they cannot be incompatible: because only if the proposition has the same meaning in two different theories, there can be a true disagreement. So, in this way, incommensurability does not really make sense.

In response to this, Kuhn adjusted his thesis. He now said partial translation between paradigms could occur, so to some extent the paradigms could communicate. But still he said fully objective choic between them was impossible. He said, next to the incommensurability coming from the lack of a common language, there is also something called "incommensurability of standards". This is the idea that different paradigms may disagree about what features a good paradigm should have, and how it should handle things, etc. So, Kuhn said, even if they can communicate, they will not be able to agree on the best paradigm. 

Kuhn's second argument had to do with an idea known as the "theory-ladenness" of data. He disagreed with the belief in "neutral" data that could show which theory is the best one, as the logical empiricists believed, because he thought neutral data did not exist. Data is always contaminated with theoretical assumptions, he thought. This idea had two important consequences for Kuhn. Firstly, it meant that a disagreement between two paradigms could not be fixed by just looking at the data or the facts, because the paradigm influences the data. So, objective choice is just not possible as there is no neutral starting point. Secondly, the idea of objective truth is shaky, because to be objectively true a theory must correspond to the facts; but according to Kuhn the facts are actually already infected by theories. So Kuhn figured truth is relative to a paradigm.

So, why did Kuhn think all data is theory-laden? He argued that perception is always conditioned by background beliefs. And also, scientists' reports are often done in very theoretical language, thus already displaying theory. 

Many philosophers agree that pure theory-neutrality is not possible. But still, there are statements that are sufficiently theory-neutral to be accepted by multiple paradigms, so the whole objectivity of paradigm shifts does not need to be completely compromised. For example, statements like "on May 14th the sun rose at 7.10 am" can be agreed on whether you believe in a heliocentric or geocentric theory. 

Not many agree when it comes to Kuhn's rejection of objective truth. However, this is greatly because of Kuhn's failure to come up with a good alternative. And when you claim that truth is paradigm-relative, is that even objective truth? Because you can not say yes or no to that question without discrediting the theory, it does not really make sense.

What can I learn about Kuhn and the rationality of science?

Kuhn's work was interpreted as very radical, and later he moderated his tone hugely. He now said he did not try to cast doubt on the rationality of science, but just wanted to offer a more realistic, historically accurate view of how science develops. When he talked about this, he claimed that there is 'no algorithm' for theory choice in science: thus, there is no set of rules which tells us which theory to choose, as was actually believed implicitly all this time. Kuhn is probably right that there is no algorithm. An element of subjective judgment, or scientific common sense, is often needed. So, if there's no algorithm, it can be concluded that scientific change is irrational, or that the conception of rationality at work is too demanding. A more relaxed concept of rationality is necessary to make sense of paradigm shifts.

What is Kuhn's legacy?

Kuhn transformed philosophy in science because he questioned things that were basically taken as the truth, and also drew attention to things that were ignored until then. He shook the philosophical world. He focused more on the historical development and also focused more on the social context in which science takes place. A sociological movement known as the 'strong program' owes much to Kuhn and is based on the idea that science should be looked at as a product of the society in which it is practiced. Strong program sociologists used some of Kuhn's ideas but were more radical and less cautious, openly rejecting the terms of truth and rationality, and being very suspicious of traditional philosophy of science. That is why there was, and even now is, some tension between philosophers and sociologists of science. 

Kuhn's work also played a role in the rise of social constructionism in humanities and social sciences. This is the idea that certain phenomena are "social constructs" instead of having an objective mind-independent existence. Some also think science is a social construct, and they often have an anti-scientific attitude. Kuhn however, though he emphasized social context, was very pro-science.