What is science?


Because of my science training and my interest in its history and philosophy I am sometimes called upon to answer the question “what is science?” Most people think that the answer should be fairly straightforward. After all science is such an important and integral part of our lives that everyone feels that they already know what it is and think that the problem of defining science is purely one of finding the right combination of words that captures their intuitive sense.

But as I said in an earlier previous posting, strictly defining something means having demarcation criteria for it, which involves developing a set of necessary and sufficient conditions, and this is extremely hard to do even for seemingly simple things like (say) defining what a dog is. So it should not be surprising that it may be harder to do for an abstract idea like science.


The absence of an agreed-upon formal definition of science has not hindered science from progressing rapidly and efficiently. Science marches on, blithely unconcerned about its lack of self-definition. People start worrying about definitions of science mainly in the context of political battles, such as those involving so-called intelligent design creationism (or IDC), because advocates of IDC have been using this lack of a formal definition to try to define science in a self-serving way so that their pet idea can be included as science, and thus taught in schools as part of the science curriculum and as an alternative to evolution.

Having a clear-cut demarcation criterion that defines science and is accepted by all would settle this question of whether IDC is science once and for all. But finding a satisfactory demarcation criterion for science has proven to be remarkably difficult.

To set about trying to find criteria that distinguishes between one class of ideas from another class, we do what we usually do in all such cases, we first set about finding all the unambiguous members of each class and see if we can extract common properties of each class.

In the case of science, we look at all the knowledge that is commonly accepted as science by everyone, and see if we can identify what is common among these areas. For example, I think everyone would agree that the subjects that come under the headings of astronomy, geology, physics, chemistry, and biology, and which are studied by university departments in reputable universities, all come under the heading of science. So any definition of science that excluded any of these areas would be clearly inadequate, just as any definition of ‘dog’ that excluded a commonly accepted breed would be dismissed as inadequate.

This kind of exercise is exactly we do when trying to define other things, like art (say). Any definition of art that excluded paintings hanging in reputable museums would be considered an inadequate definition.

Similarly, there is a general consensus that astrology, fortune-telling, and the like are not science. Any definition of science that resulted in those topics being considered science would be considered inadequate.

When we look at the history of the topics studied by people in those named disciplines that are commonly accepted as science, the first thing that we notice is that for a theory to be considered scientific it does not have to be true. Newtonian physics is commonly accepted to be scientific, although it is not considered to be universally true anymore. The phlogiston theory of combustion is considered to be scientific though it has long since been overthrown by the oxygen theory. And so on. In fact, since all knowledge is considered to be fallible and liable to change, truth is, in some sense, irrelevant to the question of whether something is scientific or not, because absolute truth cannot be established.


But there is a clear pattern that emerges about scientific theories. All the theories that are or have been considered to be science are (1) naturalistic and (2) predictive.


By predictive, I mean that all theories that are considered part of science have the quality of having some explicit mechanism or structure that enable the users of these theories to make predictions, of being able to say what one should see if one did some experiment or looked in some place under certain conditions.

Note that these two conditions are just necessary conditions and by themselves are not sufficient. (See this earlier posting for what those conditions mean.) As such they can only classify theories into “may be science” (if it meets both conditions) or “not science” (if it does not meet either or both conditions.) As such, these two conditions by themselves do not make up a satisfactory demarcation criterion. For example, the theory that if a football quarterback throws a lot of interceptions his team is likely to lose, meets both naturalistic and predictive conditions, but such theories are not usually considered part of science.

But even though we do not have rigorous demarcation criteria for science, the existence of just necessary conditions still has important implications, which I shall explore in later postings.


  1. says

    I agree that astrology is not science. I have just looked at this site: http://www.horoscopelist.com which has readings from so called top astrologers and all their predictions differ. Surely if there was scientific merit in Astrology their predictions would be at least similar assuming proper application of the theories.

  2. says

    In my humble opinion, Astrology is a science and I hope it will improve and be given the name “science” soon. There are many so called astrologers who make money from Astrology but know very little about it. They mainly contribute to Astrology being perceived as non-science subject :(

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