The short passage from Burnet and the longer one quoted from Gomperz at the end of the last chapter form the selected ‘text’, as it were, of this little book. We shall return to them later, when we shall try to answer the question: what is, then, that Greek way of thinking about the world? What are those peculiar traits, in our present scientific world view, that originated from the Greeks, whose special inventions they were, that are thus not necessary but artificial, being only historically produced and thus capable of change or modification, and which we, by ingrained habit, are liable to regard as natural and inalienable, as the only possible way of looking at the world?

However, at the moment we shall not yet enter on this main question. Rather, by way of preparing the answer, I wish to introduce the reader to parts of ancient Greek thought which I consider relevant in our context. In this I shall not adopt a chronological arrangement. For I am neither willing nor competent to write a brief history of Greek philosophy, there being so many good, modern and attractive ones (particularly Bertrand Russell's and Benjamin Farrington's) at the disposal of the reader. Instead of following the order in time let us be guided by the intrinsic connexion of the subjects.

I vividly recall reading Erwin Schrödinger's slim volume Science and Humanism some forty years ago, probably at a time while I was still a research student in Cambridge. It had a powerful influence on my subsequent thinking. Nature and the Greeks, although based on slightly earlier lectures, was not published until somewhat later, and I have to confess that I did not come across it then. Having only now read it for the first time, I find a remarkable work, of a similar force and elegance.

The two volumes go well together. Their themes relate closely to each other, being concerned with the nature of reality and with the ways in which reality has been humanly perceived since antiquity. Both books are beautifully written, and they have a particular value in enabling us to share in some of the insights of one of the most profound thinkers of this century. Not only was Schrödinger a great physicist, having given us the equation that bears his name – an equation which, according to the principles of quantum mechanics, governs the behaviour of the very basic constituents of all matter – but he thought deeply on questions of philosophy, human history and on many other issues of social importance.

Be this as it may, it seems worth our while to try to examine the matter from various angles. A point of view that I have previously touched on in these lectures and that does suggest itself is this, that our present difficulties in physical science are bound up with the notorious conceptional intricacy inherent in the idea of the continuum. But this does not tell you much. How are they bound up? What precisely is the mutual relationship?

If you envisage the development of physics in the last half-century, you get the impression that the discontinuous aspect of nature has been forced upon us very much against our will. We seemed to feel quite happy with the continuum. Max Planck was seriously frightened by the idea of a discontinuous exchange of energy, which he had introduced (1900) in order to explain the distribution of energy in black-body-radiation. He made strong efforts to weaken the hypothesis, and, if possible, to get away from it, but in vain. Twenty-five years later the inventors of wave mechanics indulged for some time in the fond hope that they had paved the way of return to a classical continuous description, but again the hope was deceptive.

On p. 12 I briefly touched upon that old crux, the apparent contradiction between the deterministic view about material events and what is called in Latin liberum arbitrium indifferentiae, in modern language free will. I suppose you all know what I mean: since my mental life is obviously bound up very closely with the physiological goings on in my body, more especially in my brain, then, if the latter are strictly and uniquely determined by physical and chemical natural laws, what about my inalienable feeling that I take decisions to act in this or that way, what about my feeling responsibility for the decision I actually do take? Is not everything I do mechanically determined in advance by the material state of affairs in my brain, including modifications caused by external bodies, and is not my feeling of liberty and responsibility deceptive?

This does strike us as a true aporia, which occurred for the first time to Democritus, who realised it fully—but left it alone; very wisely, I think. He fully realised it. While he adhered to his ‘atoms and the void’ as the only reasonable way of understanding objective nature, we have some definite utterances of his preserved, to the effect that he also realised that this whole picture of the atoms and the void was formed by the human mind on the evidence of sense perceptions, and nothing else; and other utterances where he states, almost in the words of Kant, that we know nothing about what any thing really is in itself, the ultimate truth remaining deeply in the dark.

Now I shall try to give you an idea of the way in which physicists at present endeavour to overcome this failure. One might term it an ‘emergency exit’, though it was not intended as such, but as a new theory. I mean, of course, wave mechanics. (Eddington called it ‘not a physical theory but a dodge—and a very good dodge too’.)

The situation is about as follows. The observed facts (about particles and light and all sorts of radiation and their mutual interaction) appear to be repugnant to the classical ideal of a continuous description in space and time. (Let me explain myself to the physicist by hinting at one example: Bohr's famous theory of spectral lines in 1913 had to assume that the atom makes a sudden transition from one state into another state, and that in doing so it emits a train of light waves several feet long, containing hundreds of thousands of waves and requiring for its formation a considerable time. No information about the atom during this transition can be offered.)

So the facts of observation are irreconcilable with a continuous description in space and time 5 it just seems impossible, at least in many cases.

We shall now, at last, come down to some special topics. What I have said hitherto may seem pretty long, if you consider it a mere introduction. But I hope it is of some interest in itself—and I could not avoid it. I had to make clear the situation. None of the new discoveries about which I may tell you is frightfully exciting in itself. What is exciting, novel, revolutionary, is the general attitude we are compelled to adopt on any attempt to synthesize them all.

Let us go in medias res. There is the problem of matter. What is matter? How are we to picture matter in our mind?

The first form of the question is ludicrous. (How should we say what matter is—or, if it comes to that, what electricity is—both being phenomena given to us once only?) The second form already betrays the whole change of attitude: matter is an image in our mind—mind is thus prior to matter (notwith-standing the strange empirical dependence of my mental processes on the physical data of a certain portion of matter, viz. my brain).

During the second half of the nineteenth century matter seemed to be the permanent thing to which we could cling.

It cannot be denied that the new physical aspect of nature of which I have tried to give you some idea by this example is very much more complicated than the old way which I called ‘the classical ideal of uninterrupted, continuous description’. The very serious question arises naturally: Is this new and unfamiliar way of looking at things, which is at variance with the habits of everyday thinking—is it deeply rooted in the facts of observation, so that it has come to stay and will never by got rid of again $ or is this new aspect perhaps the mark, not of objective nature, but of the setting of the human mind, of the stage that our understanding of nature has reached at present?

This is an extremely difficult question to answer, because it is not even absolutely clear what this antithesis means: objective nature and human mind. For on the one hand I undoubtedly form part of nature, while on the other hand objective nature is known to me as a phenomenon of my mind only. Another point that we must keep in mind in pondering this question is this: that one is very easily deceived into regarding an acquired habit of thought as a peremptory postulate imposed by our mind on any theory of the physical world.

Turning now to the philosophers usually classed together under the name of the Milesian School (Thales, Anaximander, Anaximenes) and, in the next chapter, to some more or less connected with them (Heraclitus, Xenophanes), then to the atomists (Leucippus, Democritus), let me point out two things. First, the order in regard to the preceding chapter is not chronological; the floruit of the three Ionian ‘physiologoi’ (Thales, Anaximander, Anaximenes) is approximately dated at 585, 565, 545 b.c. respectively, as against Pythagoras 532 b.c. Secondly, I wish to point out the double role that this whole group plays in our present context. They are a group of definitely scientific outlook and aims, just as the Pythagoreans were, but opposed to them as regards the competition ‘Reason v. Senses’, explained in our second chapter. They take the world as given to us by our senses and try to explain it, not bothering about the precepts of reason any more than the man in the street does, from whose way of thinking theirs is a direct descendant. Indeed it frequently starts from problems or analogies of handicraft and serves practical applications in navigation, mapping, triangulation. On the other hand let me remind the reader about our main problem, which will be to find out the special and somewhat artificial features of present-day science that are supposed (Gomperz, Burnet) to originate from Greek philosophy.

But let us return to our subject proper. A much more serious and interesting attempt to explain the difficulty away was founded by Bohr and Heisenberg on the idea, mentioned above, that there is an unavoidable and uncontrollable mutual interaction between the observer and the observed physical object. Their ratiocination is briefly as follows. The alleged paradox consists in this, that according to the mechanistic view, by procuring an exact knowledge of the configuration and velocities of all the elementary particles in a man's body, including his brain, one could predict his voluntary actions—which thereby cease to be. what he believes them to be, namely voluntary. The fact that we cannot actually procure this detailed knowledge is no great help. Even the theoretical predictability shocks us.

To this Bohr answers that the knowledge cannot even be procured in principle, not even in theory, because such accurate observation would involve so strong an interference with ‘the object’ (the man's body) as to dissociate it into single particles—in fact kill him so efficiently that not even a corpse would be left for burial. At any rate, no prediction of behaviour would result, before the ‘object’ is far beyond the state of exhibiting any voluntary behaviour.

These are four public lectures which were delivered under the auspices of the Dublin Institute for Advanced Studies at University College Dublin in February, 1950 under the title ‘Science as a Constituent of Humanism’. Neither this nor the abbreviated title chosen here adequately covers the whole, but rather the first sections only. In the remaining part, from p. 11 onward, I intend to depict the present situation in physics as it has gradually developed in the current century $ to depict it from the point of view expressed in the title and in the earlier part, thus giving, as it were, an example of how I am looking on scientific effort: as forming part of man's endeavour to grasp the human situation.

My thanks are due to the Cambridge University Press for the rapid production of this booklet and to Miss Mary Houston from the Dublin Institute for designing the figures and reading the proofs.

What is the value of scientific research? Everybody knows that in our days more than ever before a man or a woman who wishes to make a genuine contribution to the advancement of science has to specialize: which means to intensify one's endeavour to learn all that is known within a certain narrow domain and then to try and increase this knowledge by one's own work—by studies, experiments, and thinking. Being engaged in such specialized activity one naturally at times stops to think what it is good for. Has the promotion of knowledge within a narrow domain any value in itself? Has the sum total of achievements in all the several branches of one science—say of physics, or chemistry, or botany, or zoology—any value in itself—or perhaps the sum total of the achievements of all the sciences together—and what value has it?

A great many people, particularly those not deeply interested in science, are inclined to answer this question by pointing to the practical consequences of scientific achievements in transforming technology, industry, engineering, etc., in fact in changing our whole way of life beyond recognition in the course of less than two centuries, with further and even more rapid changes to be expected in the time to come.