The Nature of Scientific Explanation


It is the job of science to explain things but how exactly does that explanation work / what kind of explanation does science actually offer to us. To begin answering this question we need to first become aware that there are many kinds of explanation; they are the answers to many kinds of question. Some examples follow below:


1.       What is photosynthesis? What is an ombudsman? What is heuristics? Here the explanation would be a definition of these terms.


2.       What does this fire insurance policy mean? Can you explain Finnegans Wake? Here the explanation would be a paraphrase of these documents, which would restate the sense in simpler or more familiar words.


3.       Will you explain chess to me? The explanation here would be to state the rules of the game.


4.       Why is there no greatest prime number? Why is the sum of the interior angles of a Euclidean triangle 1800? Here the explanation would be the analysis of what is logically entailed by certain postulates of logic and mathematics.


5.       How do you fly a kite? How do you ski? The explanation here would be a practical demonstration of a skill or a technique; it might not require language.


6.       Why did Brutus stab Caesar? This explanation would provide Brutus’ reasons, motives, and beliefs.


7.       Why are snow and milk alike? The explanation here would require reference to the metaphysical universal “whiteness” in which both substances participate.


Thus, there are various ways in which an explanation may be given. One of my favorites appears in a story by Ring Lardner: “‘Why are we going in there again, daddy?’ ‘Shut up,’ his father explained.” All of these explanations work by releasing the tension that provoked the question. It evokes the “aha!” response: oh, so Brutus thought Caesar wanted to be emperor! so the Trojan horse was full of soldiers! so Miss Prism was the nurse! so there was sabotage on the plane! If the puzzlement is not in fact eliminated, the explanation is not accepted. Byron wrote, of Coleridge’s ‘Explaining Metaphysics to the Nation’ “I wish he would explain his explanation.”


So how does explanation work in Science? Ideally Science explains a fact by embedding it within a general law from which, along with the particular conditions involved, the fact to be explained may be logically deduced. Thus:

  1. Why did the pond freeze? Because the temperature dropped below 32°F., and water freezes at 32°F.
  2. Why did the pipe rust? Because it is made of iron, and iron combines chemically with the oxygen in the air.
  3. Why did the water pipes burst last winter? Because water expands when it freezes.
  4. Why did Bert catch malaria? Because he was bitten by the anopheles mosquito, which is the carrier of that disease.
  5. Why was there an eclipse of the sun? Because of the laws of gravitation and the orbits of the planets.


In each case, the particular fact is explained by being comprehended under, and derived from, a general law. The scientist explains what happens by devising concepts (e.g., temperature, oxidation, and gravitation) to describe particular experiences, and by supplying a framework of covering laws from which, in conjunction with the specific conditions involved, we may make inferences about what it is that we want to have explained.


In some cases Science also explains something new by reducing it to something simpler that we already understand. This is called reductionism and science abounds with good examples of how reductionism helps us explain something: when sound was reduced to a wave in the air, all that was previously known about water waves could be applied to sound waves; lightning has been reduced to electricity; heat to molecular motion; magnetism to molecular alignment … etc.


The term reductionism is occasionally attacked by some as a bad thing and this is often when scientists try to explain something human, beautiful or special in terms of something simple, biological and ugly – for example that your mind is really just a product of your brain. However, it is important to bear in mind that when you reduce one thing to another you only make a conceptual link between the two things to help you understand the second by using ideas that you already have about the first. Thus, saying that the mind is a product of brain activity is meant to help us understand what the mind is using what we already understand about the physiology of the brain it is not meant to ‘get rid’ of the mind. Heat is as real and as hot as it ever was, even though it is really only an aspect of molecular motion and in the same way the mind is as real as ever, even though it is really only an aspect of brain activity.


Science is also said sometimes to have explained something when it can be used to predict the behaviour of that thing. For example we have explained why dropped rocks fall because the theory of Gravity allows us to predict that rocks will fall when dropped on the Earth, but they won’t in space, but that they will again on the Moon.


So it seems that there are at least three different ways in which science can be said to explain something, although the first is by far the commonest. While we are on the subject, however, it will be useful to consider some common misconceptions about scientific explanation:


1.       It is sometimes said that science describes, rather than explains. This point is usually raised by those who would prefer to explain that Bert caught malaria because he deceived his wife, or that the pond froze so that the children could skate. On November 1, 1755, an earthquake in Lisbon killed some flfteeen thousand people within six minutes and demolished thirty churches and a thousand homes. The quake was explained by the theologian John Wesley in a sermon on “The Cause and Cure of Earthquake” as the result of sin, which he said “is the moral cause of earthquakes, whatever their natural cause may be . . . they are the effect of that curse which was brought upon the earth by the original transgression” of Adam and Eve. Actually, no sharp line can be drawn between description and explanation. If the scientific explanations of why the pond froze and why there was an eclipse are really only descriptions, what, then, would an explanation be? How else would you explain these events?


2.       It is sometimes said that science explains the strange by the familiar; but typically the reverse is the case. Such familiar phenomena as rust, sunrise, tides, illness, family resemblance, and so on, are explained by such unfamiliar concepts as oxidation, gravitational attraction, invisible germs, and genes.


3.       Scientific explanation is not the same as “understanding” in the sense in which it is said, for example, that D. H. Lawrence understood women, or that T. E. Lawrence understood the Arab mentality, or that an experienced nurse understands children. Such understanding is more like knowledge by acquaintance or like knowing how than like science.


4.       A scientific explanation need not be a causal law. It may be a law of simultaneous existence rather than of succession. Boyle’s Law, for example, associates the pressure of a gas with its volume, but pressure and volume are not cause and effect.



Adapted from Reuben Abel’s ‘Man is the Measure’ (Chapter 10)