Does Science Need Philosophy?

I was invited to give a lecture at the London School of Economics on the theme: ‘Does Science Need Philosophy?’. It was intended to be the closing talk at the European Congress on the Philosophy of Physics, and it was meant to respond to a recent series of very negative public comments about philosophy, by some very well-known colleagues of mine. Stephen Hawking had written, for instance, that philosophy was dead now that we had science, and a chapter in the most recent book by the Nobel Prize winner Steven Weinberg was entitled ‘Against Philosophy’. I accepted the invitation out of solidarity with philosophers, though without really knowing what I was going to say. I started studying, and soon had a marvellous stroke of luck. Like a schoolboy who has been set a difficult piece of homework and stumbles across someone else’s perfect answer to copy, I found that the theme had already been excellently developed in a little-known text by a young man undoubtedly more gifted than myself: Aristotle.

In the fourth century BC, the sons of the best families in Athens studied in Plato’s Academy. But the Academy was not the only school in the city: others challenged its primacy, and among these rival academies the one run by Isocrates stood out. Between the schools of Plato and Isocrates there was a fierce rivalry, something like that between Oxford and Cambridge. But the rivalry was not so much regarding quality as method. Education in the Academy was based on the ideas of Plato, who maintained that in everything it was crucial to study the fundamentals. You didn’t learn how to be a court judge, to carve a statue or to govern a city – but rather inquired into the nature of justice, of beauty and of the ideal city. Plato had found a term for his method that would go on to enjoy some considerable success – ‘philosophy’, which originally referred to this way of educating the young and encouraging the development of their knowledge. Isocrates, in his corner, contested this ‘philosophical’ approach, considering it to be useless and unfruitful. He wrote, for example, that

Those who study philosophy may be able to actually do something, but they will invariably do it worse than those who participate directly in practical activities. Whoever pays no attention to philosophical discussions and is inducted directly into a practical activity will be much more successful in every case. As far as the arts and sciences are concerned, philosophy is completely useless.

These are more or less the same sentiments expressed by Hawking and by Weinberg in order to criticize philosophy now. But to this criticism a brilliant reply was given by a young student at the Academy. Aristotle – for it was he – couched that reply in the form of a dialogue, Platonic style, and gave it the title Protrepticus, which roughly means an ‘invitation’ (to philosophy). Aristotle responds to the criticisms levelled by Isocrates, and discusses why philosophy, the study of fundamentals and of abstract concepts, is useful to the arts and concrete sciences. Precisely the theme, in other words, assigned to me for my lecture.

The Protrepticus was a well-known text in antiquity, cited by numerous authors. A consistent body of Aristotle’s work has come down to us, but all from a much later period, written after he had left the Academy in Athens. He spends time on the island of Lesbos studying fish and other animals, and in the process founds the science of biology; he becomes tutor to the young future master of the world, Alexander, and to the group of friends who will later divide the empire between them and form the ruling families of the Hellenistic world, filling it with Aristotelian ideas and values. He returns to Athens, where he opens his own school, the Lyceum. The texts by Aristotle that have survived are probably the textbooks of the Lyceum, not one of them in dialogue form. The youthful dialogue on the usefulness of philosophy was lost in the cultural disaster that the conversion of the Roman Empire to Christianity entailed, with the systematic and brutal destruction of pagan thought, inaugurated by the Emperor Theodosius in the fourth century (with the subsequent destruction of the library of Alexandria, which can probably be attributed to Theophilus and his successor, St Cyril) and continuing unabated all the way to Justinian, who in 529 shut down the last incarnation of the Academy in Athens.

The modern reconstruction of the text of Protrepticus is an ongoing source of controversy. It is based mainly on an extensive work by Iamblichus, the Greek author of late antiquity who systematically copies and incorporates whole pages of work by the author whose ideas he is engaged in expounding. This makes it possible to put together from this work a plausible reconstruction of Aristotle’s original dialogue. To prepare for my lecture, I read it. It turned out to be quite a surprise: the arguments used by Aristotle regarding the usefulness of philosophy for science are still completely relevant. All I had to do was copy them out myself and adjust them a little. Here they are.

The first argument is the most amusing, but it is also very subtle. Those who criticize the usefulness of philosophy for science, Aristotle has noticed, are not doing science: they are doing philosophy.

When Hawking and Weinberg do their great physics, they are scientists. When they write that philosophy is useless for science, they are not attempting to resolve a physics problem: they are merely reflecting on what may be considered useful, what methodology and conceptual structure is appropriate for doing science. Reflecting in this way is a useful enterprise and is precisely what philosophy does. The arrogantly pragmatic and ‘anti-philosophical’ attitude of Hawking and Weinberg, in fact, has its origins in … philosophy! We can easily trace it back to the philosophers of science who influenced their generation of scientists: the logical positivists with their anti-metaphysical rhetoric, followed by Karl Popper and Thomas Kuhn. Hawking and Weinberg are repeating ideas that come from the philosophy of science. Not only are they not aware of this, but they are not even up to date, since the philosophy of science has made some useful progress since Popper and Kuhn …

Aristotle’s second argument is the most direct: the analysis of fundamentals has in fact had an influence on science.

If in the fourth century this might have seemed like wishful thinking, today it is an undeniable historical fact: the influence of philosophical thought on the finest Western science has been deep and persistent. Newton would not have existed without Descartes; Einstein learned directly from Leibniz, Berkeley and Mach, and from the philosophical writings of Poincaré; not to mention the fact that he would read Schopenhauer before falling asleep at night, and had read Kant’s three Critiques before he was fifteen years old. The influence of positivism and of Mach upon Werner Heisenberg, the discoverer of quantum mechanics, is quite clear from his articles. And post-war American physics is inconceivable without the influence of pragmatism. And so on. A full list of this kind would be a very long one. Philosophical thought opens windows, frees us from prejudices, reveals incongruities and leaps of logic, suggests new methodological approaches, and in general opens up the minds of scientists to new possibilities. It has always done so in the past, and it continues to do so.

The reason that philosophical thought has this important role is the fact that the scientist is not a rational being with a fixed conceptual baggage who works on data and theories: he is a real being whose ‘conceptual baggage’ is continuously evolving as our knowledge gradually grows. Elaboration of general conceptual structure is what philosophers specialize in. It is above all in the area of scientific methodology, which is anything but fixed and static, that philosophy tends to interface with science. ‘Philosophy,’ writes Aristotle, ‘offers a guide to how research should be conducted.’

The third of Aristotle’s arguments is a simple observation: science needs philosophy ‘especially where perplexities are greatest’.

When science undergoes periods of radical change during which fundamentals are questioned, it is most in need of philosophy. A prime example of this is our current moment, in which fundamental physics faces the problem of quantum gravity (on which I work), where our notions of space and time are once again under discussion, and the old debate on space and on time – from Aristotle to Kant, and all the way down to David Lewis – has become relevant again.

No, philosophy is hardly useless to science. It is, on the contrary, a vital source of inspiration, criticism and ideas.

But if the great science of the past was nourished by philosophy, it is also true that the great philosophy of the past was passionately nourished by science. Hume and Kant are incomprehensible without Newton. Or Descartes without Copernicus; or Aristotle without the Preocratic physicists; or Quine without Einstein’s relativity. Even philosophers of the stature of Husserl and Hegel, who seem rather more distant from contemporary science, drew on the science of their time as a model of reference.

To shut one’s eyes to contemporary scientific knowledge, as, alas, some philosophy in some European countries has done, is in my opinion simply ignorant. Even worse is the attitude of those currents in philosophy that consider scientific knowledge to be ‘inauthentic’, or of a lower order – or regard it as an arbitrary organization of thought that is no more effective than others. They remind me of two retired old men on a park bench: one mutters ‘Scientists are so presumptuous. They think they can understand consciousness, or the origins of the universe!’, and the other one grumbles: ‘What arrogance. It’s obvious they’ll never succeed! To understand these things, of course, it takes … the two of us!’

Our knowledge is incomplete, but it is organic: it is constantly growing, and every part of it has influence over every other part. A science that closes its ears to philosophy fades into superficiality; a philosophy that pays no attention to the scientific knowledge of its time is obtuse and sterile. It betrays its own deepest roots, which are evident in the etymology of philosophy: the love of knowledge.