Samir Okasha, Philosophy of Science: A Very Short Introduction (Oxford, UK: Oxford University Press, 2002)
Chapter 1. What is Science?
First comes a quick survey of the history of science from Copernicus to Watson and Crick.
“The principal task of philosophy of science is to analyse the methods of enquiry used in the various sciences.” Descartes, Newton, and Einstein [were] deeply interested in philosophical questions about how science should proceed, what methods of enquiry it should use, how much confidence we should place in those methods, whether there are limits to scientific knowledge, and so on.” (12)
It would be nice to define science, but we don’t seem to be able to do that, because the term covers such a variety of disciplines and methods.
Karl Popper (13-17, 23)proposed a criterion for science: Science must be falsifiable. In other words, it must make predictions that can be shown to be false. We can find evidence that is consistent with a theory, but such evidence does not prove that the theory might be later shown to be false. But if we have even one case where the theory predicts something false, we know that the theory is wrong. Therefore our energies in testing a theory must go toward trying to falsify it.
Popper’s favorite examples of pseudo-science were Freudian psychoanalysis and Marxian political economy. Since these “sciences” could come up with explanations for completely opposite responses to a condition (revolt against oppression or identify with the oppressor; a son’s being angry at the father or idealizing the father), they did not make predictions which could be falsified .
Popper’s criterion, however, does not match how science actually works. Sometimes a theory makes predictions which are falsified and yet the scientist continues to work with the theory. If every theory were dropped because a single experiment did not confirm the prediction, we would quickly be left with no theories at all.
One of the more important alternatives to Popper's philosophy of science is is not discussed here but referred to later in the text. Imre Lakatos explained that scientific research programs prove more or less progressive over time, and their structure is to have a “hard core” hypothesis which is hardly allowed to be falsified combined with “auxiliary” hypotheses which are more readily falsifiable. Thus Darwin continued to develop his account of evolution despite finding that he had to reject some particular mechanisms that he thought explained evolution.
There is no criterion we can strictly rely upon, so Wittgenstein’s “family resemblance” approach, which he applied to the impossibility of defining a game may be the best we can do.
Chapter 2. Scientific Reasoning. Some reasoning in science aims at deductive validity: If the premises are true, the conclusion must be true (18). (This ape is a mammal, therefore it must have the characteristics common to all mammals.) Much reasoning in science, however, is inductive (19-23). For example, we make a generalization about all things of a certain kind based on our examination of some of those things, all of which show a particular characteristic.
David Hume (Scottish, 1711-76) raised a famous problem about induction. We cannot prove the validity of induction without presupposing “the uniformity of nature,” which means that we are presupposing the very thing we are trying to prove.
Edmund Husserl (German, 1859-1938), not mentioned in the text, clarified the phenomenon. Perception tacitly anticipates future experience as, for example, I look at a rock, turning it around in my hand, seeing one side after another. I can be surprised, of course, but my unspoken (“prepredicative”) anticipation (“protention”) is that my continued perception of the rock will continue to confirm the sense of the rock that I got from the beginning. This deep fact about the perception of things is no puzzle; nor does it involve any inference. There is no premise, no conclusion. The puzzle only arises when someone tries to prove something. (Perhaps—this is Jeff’s thought—Husserl uncovered a depth where any attempt to prove assumes too much or proves too little.)
Peter Strawson “argued that induction is so fundamental to how we think and reason that it’s not the sort of thing that could be justified [by reason]” (28). To try to prove it is a mistake, like asking for a proof of the legality of law. Frank Ramsey regarded the attempt to prove the validity of induction as misguided.
Another kind of argument that is important in daily life and in science is “inference to the best explanation.” (A mouse must have eaten that cheese.) IBE appeals to some explanatory factor (note the examples of Darwin and Einstein, 31-32). Philosophers debate about whether this is an extension of inductive argument or the kind of argument that underlies the inductive generalization mentioned previously. When different explanations compete, it is common to prefer the simpler explanation, although we cannot assume that simplicity (or “parsimony”) is a guarantee of correctness (33).
One attempt to explain induction appeals to probability. There are three competing interpretations of probability, and none of them enables us to prove that induction is valid. The first interpretation takes probability as simply a measure of the frequency of a phenomenon (flipping the coin yields heads about half the time). That does not explain what Hume called “our animal faith” in induction. The second interpretation is that the number we use to express the probability of some event occurring is merely a symbol of our subjective belief that the event will occur. This does not explain our confidence in the uniformity of nature. The third interpretation is that there is a logic implicit in the structure of the phenomenon that makes the probability estimate reasonable. But so many problems (not specifically mentioned) have been raised to this idea that most philosophers have abandoned the idea.
The “problem of induction” “leads us into a thicket of interesting questions about the structure of scientific reasoning, the nature of rationality, the appropriate degree of confidence to place in science, the interpretation of probability, and more. . . . In grappling with [such philosophical questions] we learn much about the nature and limits of scientific knowledge” (38-39).
Chapter 3. Explanation in science. Hempel’s covering law interpretation of scientific explanation (42) fits many cases, but fails both as a necessary condition and as a sufficient condition for scientific explanation. Some scientists turned to causality as the key to scientific explanation. Hume’s empiricism, however, cast doubt on the very idea of causation as a metaphysical fiction going beyond what we really experience: event x followed by event y (even if we are talking about event types that are continually observed to follow each other). Of course not every scientific statement expresses or suggests causation, but many do.
This leads to the question of how much science can explain. But even if everything is made out of the material components that physics studies [in other words, if materialism is true and there is no reality to life or mind or spirit that is more than matter], it is still the case that not every science can be reduced to physics. This is because, among other possible reasons, there are things on different levels that have multiple physical realization—in other words, can be so differently made that physics is unable effectively to generate a reductionist account of these phenomena.
See p. 35 in “Scientific living” for a quick word about reductionism. There are three types. Metaphysical reductionism in religion says that God is nothing but a projection of the human mind. The reduction of one science to another (challenged by Okasha) is illustrated by the claim that psychology will some day be explained by biochemistry. And methodological reductionism says that, say, for the purposes of this research program, we shall take religious experience simply as reflected in the brain, so that neuroscience will be able to say talk of mind is, in reality, just a way of talking about brain process. Reductionism in biology says that biology is a convenient shorthand for what physics will eventually be able to explain definitively. The contrasting view is that reductionism tells part of the story but not the heart of the story. Recall Socrates’ statement that factors of mind, not body, explained his remaining in prison. Recall Descartes’ clear recognition of the reality of mind. Okasha makes it an empirical question how much science will someday be able to explain. The origin of life? Consciousness? Are you persuaded that you should keep your philosophical anthropology in suspense like that? Or how do you think about these things? The natural thing for beginners in philosophy to do is to suspend judgment, since one feels unready to enter into the fray. But you have intuitions regarding these things, and I encourage you to deepen you contact with them and to articulate your best current thinking.