Stamp Collecting in Science - Symposia: The Online Philosophy Journal

Stamp Collecting in Science

"In science, there is only physics. All the rest is stamp collecting."

Such are the famous words of Ernest Rutherford, the early 20^th century physicist and pioneer of the orbital theory of the atom. Rutherford’s quote appeals to the often-held view that physics is the one elementary science that deals with the basic laws of nature, whereas all other sciences are merely involved in the arbitrary classification of phenomena that are, in principle, reducible to these basic laws. In this essay, I argue against this viewpoint, and propose that other sciences can also be considered to be elementary in their own right.

It is widely believed that since the laws postulated by physics are considered to be basic, the phenomena dealt with by other sciences can be explained with them. For example, biology deals with living organisms. An organism’s structure is composed of matter. The dynamics of matter follow the laws of physics, and so, in principle, an organism’s biology can be explained with these laws. Of course, this is not feasible in practice, since an organism’s biology is very complex. Nevertheless, the construction of biological theories presupposes the validity of physical laws, and so biology is not considered by many to be as elementary as physics. However, upon closer analysis, it becomes apparent that the construction of physical theories and postulation of laws in physics also presupposes the validity of a number of assumptions. Some of these assumptions may have no metaphysical justification, but one’s belief in the laws postulated by physics requires one to presuppose these assumptions as being valid.

An example of such an assumption is the method of induction. This is the extrapolation of an observed pattern to postulate a general law about the unobserved. For example, in my experience thus far, the sun has risen every day, and, on this basis, I conclude that the sun rises every day, or, at least, that the sun will rise tomorrow. Since I have not yet observed whether the sun will rise tomorrow, this extrapolation is not entailed by my immediate experience. Furthermore, there is no logical entailment from the sun having risen previously to the sun rising tomorrow, for it is logically conceivable that in a possible world in which the sun has risen every day so far, the sun will not rise tomorrow. One could argue that whenever I had previously induced that the sun would rise the following day, my experience of it actually rising the following day confirmed the validity of my induction, and so I continue to assume that the sun will rise tomorrow, because this assumption has been right so far. However, as Hume shrewdly argued, this provides no justification whatsoever, for what is being said is that in my experience thus far, induction has been valid, and, on this basis, I conclude that induction will continue be valid. We can see that this statement, itself, is an inductive inference. It is attempting to justify induction via a method of induction, and, thus, fails, due to this vicious circularity. And so, Hume has shown that we have no metaphysical justification for our inductive practices.

Another example of such an assumption is the principle of Ockham’s razor. This is named after the mediæval philosopher William of Ockham, and states that in the formulation of a theory, one should not multiply the number of properties beyond what is necessary to explain the phenomena, or, in short, that simpler theories are to be favoured over complex ones. The construction of a theory from data is generally a non-deductive procedure. In other words, the theory goes beyond the data, such that it is not entailed by it, but accounts for and unifies it. What follows from this is that theories are underdetermined by data, or, in other words, since the empirical data does not entail the theory, there can be several different competing theories that each succeeds in accounting for the data. Since each competing theory succeeds in accounting for the data, a scientist cannot select one theory from a set of theories solely from the data, but, rather, extra premises beyond the data, such as simplicity, are required to select a theory in favour of its rivals. Although simplicity is a valid reason to favour one theory over another, it is not necessarily a truth-conducive virtue. Just because one theory is simpler than another, it does not mean that is it more likely to be true. As Bas van Fraassen argues in his book, The Scientific Image, the assumption that simple theories are more likely to be true is unjustified, since it is based on the groundless assumption that the truth is simple. And so, simplicity is not an indicator of truth. Rather, van Fraassen argues that it is a pragmatic virtue. When presented with two empirically equivalent theories, the scientist would choose the simpler one, specifically because it is more convenient. Simpler theories are easier to understand, communicate, and draw conclusions from, but this does not make them more likely to be true.

The laws postulated by physics are dependent on the practice of induction, for they are essentially generalisations assertions about the unobserved, extrapolated from patterns that have been observed. Physical theories are also dependent on Ockham’s razor, for the simplest and most parsimonious explanation of the phenomena is sought. Therefore, the validity of such assumptions as the method of induction and Ockham’s razor is something that must be presupposed if one is to believe in the laws postulated by physics. However, as we have seen, these assumptions are not valid a priori, but their metaphysical validity is questionable. Therefore, a philosopher of science could argue that physics is not necessarily as elementary as traditionally considered, since it is dependent on deeper assumptions which themselves can be scrutinised. Similarly, it could be argued that mathematics is not necessarily as elementary as traditionally considered, since it presupposes the validity of a set of axioms that may not themselves be metaphysically justified.

It follows that physics and mathematics can only be considered to be elementary, and their laws basic, if the validity of the assumptions they are based on is presupposed without question. But, surely then, other sciences, such as biology, can also be considered to be elementary, with respect to the phenomena they are investigating, if the validity of the laws of physics and mathematics is presupposed without question. As I mentioned earlier, physics deals with the dynamics of matter, but not with the behaviour of organisms, because the behaviour of organisms is incredibly complex when considered in terms of dynamics of matter. Therefore, the behaviour of organisms is dealt with by biology, which constructs its own theories and postulates its own laws. These theories and laws may presuppose the validity of physical theories and laws, but I argue that this does not mean that they cannot be basic. After all, as we have seen, these physical theories and laws presuppose the validity of a set of assumptions, but are still considered to be basic with respect to the phenomena they deal with. Likewise, biological theories and laws deal with phenomena that physical theories and laws do not deal with, such as the behaviour of organisms, and so can be considered to be basic with respect to these phenomena.

I would even go further to argue that there are some laws in biology that are not reducible to the laws postulated by physics. This is, perhaps, due to the abstract or emergent nature of these laws. An example is Darwin’s law of natural selection. This is the process by which heritable or transmissible traits that are favourable survive and become commoner in successive generations, while traits that are unfavourable cease to survive and become less common. Darwin applied this law to explain the evolution of organisms over generations. Indeed, one may argue that since it is an organism’s physical structure that allows it to pass on favourable traits to the next generation, natural selection can be explained in terms of physical laws, but I argue that this isn’t necessarily so. In his book, The Conscious Mind, David Chalmers proposes a possible world in which there are non-physical beings, composed of ectoplasm, which reproduce like humans and pass on heritable traits to successive generations. In other words, the reproduction of these beings follows the biological laws of Mendelian inheritance and natural selection. However, since these beings are non-physical and not composed of matter like humans are, they cannot be said to follow physical laws. Therefore, the biological law of natural selection is independent of and cannot be reduced down to physical laws, and so can be considered to be basic.

Another example, this time closer to earth, is the application of natural selection to phenomena that are not genes, such as ideas. Richard Dawkins coined the term ‘meme’ to refer to such an idea that is transmitted from one mind to another. The suggestion is that the ideas that are successful persist and perpetuate, whereas the ideas that are unsuccessful perish. This suggests that natural selection, as proposed by Daniel Dennett, is substrate-neutral. In other words, it is a law that applies, regardless of physical configuration. Again, this shows that although individual examples of natural selection, such as the passing on of an organism’s genes to the next generation, may be reducible to physical laws, natural selection itself, as an abstract law, is not. It can, therefore, be considered to be a basic law, and biology elementary with respect to phenomena that follow it, such as organisms.

In this essay, I have argued against the view that only physics is elementary and all other sciences are just “stamp collecting”. Physics, too, is based on questionable assumptions, and can only be considered to be elementary if the validity of these assumptions is presupposed. Furthermore, other sciences, such as biology, can be considered to be elementary with respect to the phenomena they are investigating, and to postulate basic laws about these phenomena. Therefore, in contrast to the traditional hierarchical view that physics is elementary and all other sciences can be reduced down to it, I am advocating a contextual view that different sciences are elementary with respect to different phenomena. Physics is elementary with respect to physical phenomena, chemistry with respect to chemical phenomena, and biology with respect to biological phenomena. And, although there is much overlap between the different disciplines, they are, at present, different fields of endeavour, and so each presupposes the validity of the others with respect to their respective phenomena.

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