This was the Presidential Address delivered to the Aristotelian Society in October 1958.
Bryan Magee's story of the lecture
This is recorded in his book Confessions of a Philosopher.
"At that time there were only two books by him in the English language: The Open Society and its Enemies and The Poverty of Historicism. They caused me to think of him as a political philosopher, albeit a great one... I was curious to see him in the flesh."
"I listened to his paper utterly engrossed -- and to the ensuing discussion with disbelief and dismay. The main contention [of the paper] is that the only practicable way of expanding human knowledge is by an unending feedback process of criticism. Put like that it may seem self-evident, but the real clout of the thesis lies in what it denies. It denies that we can get far if we attempt to base the extension of our knowledge on observation and experiment."
"The other theme of the lecture concerned the pioneering role of the pre-Socratic philosophers in developing the speculative and critical approach to cosmology. Magee considered that this historical thesis was interesting and challenging but not earth-shattering. The real punch of the lecture was in the theory of knowledge and its growth."
"If the method [of conjecture and refutation] is valid it overthrows an empirical tradition in philosophy of several hundred years standing, a tradition whose most important single tenet is that all our knowledge of the world must begin with experience. It is therefore, despite appearances, a theory that is radical -- revolutionary in a historic sense, and epic in its implications. It demolishes, almost incidentally, hundreds of years of philosophizing... I was intellectually thrilled by the argument... and agog to see it pounced on by this particular audience which contained some of the most distinguished philosophers in Britain most of whom were identified, and identified themselves, with empiricism."
"I simply could not believe it when, in the question and answer period, not a single person raised this issue or referred to it. The entire discussion, which became impassioned, turned on whether or not this or that particular pre-Socratic philosopher had been correctly represented by Popper, which in turn meant arguing about whether an important fragment might be better understood in a different way..."
"When I got home I wrote letter to Popper. In it I said that although the intellectual frivolity of the audience was inexcusable, he himself was partly to blame for what had occurred. Instead of presenting his revolutionary idea head-on, he had presented it indirectly, in the form of a historical claim about the pre-Socratics... He had, I went on, made the same mistake in the way that he had written The Open Society, with similar consequences. Instead of presenting the most important arguments directly, he had put them forward in the course of discussing other people's ideas, with the result that most academics came away from the book thinking that it was about Plato and Marx... His ideas were immensely important, but he was presenting them in a way that almost ensured that they would be misunderstood."
The original paper is fairly short and in the collection there is a lengthy appendix which is a reply to two classical scholars who challenged Popper's interpretation of the pre-Socratic fragments and also his views on the way that scientific knowledge advances.
The paper has 12 sections, some of them quite brief. In the first Popper makes a bid for a simple theory of knowledge and a return to cosmology, to attempts to understand the world we live in, including ourselves as a part of the world.
"For me, both philosophy and science lose all their attraction when the give up that pursuit [of knowledge and understanding of the world] -- when they become specialisms and cease to see, and to wonder at, the riddles of our world. Specialization maybe a great temptation for the scientist. For the philosopher it is the mortal sin."
In the second section he introduced himself as an amateur student of the pre-Socratics "completely out of my depth when an expert begins to argue which words or phrases Heraclitus might, and which he could not possibly, have used". He also dissociated himself from the belief, which he attributed to Bacon, that science should start from observations of simple things like an orange. He prefers the notion that Western science started with bold theories about the world, not with collected observations of oranges.
In sections III to VIII he sketched the rapid, speculative evolution of theories about the relationship of the earth to its surrounds. First Thales suggested that the earth is floating in water like a ship. His student Anixamander suggested an alternative theory, that the earth is not held up by anything, but is a drum-shaped object that stays in place because it is equally distant from all other things.
"As to the Presocratics, I assert that there is the most perfect possible continuity of thought between their theories and the later developments in physics. Whether they are called philosophers, or pre-scientists, or scientists, matters very little, I think. But I do assert that Anaximander's theory cleared the way for the theories of Aristarchus, Copernicus, Kepler and Galileo. It is not that he merely 'influenced' these later thinkers; 'influence' is a very superficial category. I would rather put it like this: Anaximander's achievement is valuable in itself, like a work of art. Besides, his achievement made other achievements possible, among them those of the great scientists mentioned."
"The critical discussion of Anaximander's worldview led to the serious consideration of the general problem of change, a problem which became the central problem of Greek cosmology and resulted in the work of Democritus, Parmenides, Zeno and Heraclitus. Parmenides is a particular favorite of Popper, who credits him with the first hypothetico-deductive theory of the world. When Popper engaged in a debate with Einstein, he called Einstein 'Parmenides" to draw attention to some aspects of their theories which Popper considered they held in common."
In section IX he lamented that the significance of this exciting story was being "buried under the mounting heap of the minutiae of textual criticism". I wonder if he said that in the lecture or added it in later revisions for publication?
In section X he attempted to substantiate that view with some heavy criticism of two experts in the field (Kirk and Raven) who he claimed were not interpreting the ancient texts correctly.
In sections XI and XI he presented the central theses of the speech:
The central theses
First, the great achievement of the ancient Greeks was their discovery or invention of the tradition of critical discussion.
Second, the tradition of critical discussion is the only way to expand our knowledge.
The first achievement was to transform the function of a school. The usual function of schools was (and is) to impart definite doctrines. "A school of this kind never admits a new idea. New ideas are heresies, and lead to schisms... There cannot, of course, be any rational discussion in a school of this kind".
An early example of a school of this kind was the religious order founded by Pythagoras, with a characteristic way of life and a secret doctrine. But something very different happened in the school started by Thales, where students challenged their teachers and set forth radical new doctrines without being expelled.
[As an aside, many people would like to see more written about the "Popper school" and the extent to which this deviated from the Popperian tenets of critical discussion of the ideas of the teacher. Joe Agassi wrote a book about his tormented relationship with Popper and he pointed out that Popper's personal behaviour was often and scandalously used as an excuse by philosophers of rival schools to refrain from coming to grips with Popper's ideas.]
This is the tradition which Popper claimed was rediscovered and consciously revived in the Renaissance, especially by Galileo. That led Popper to his final and most important thesis, that the critical method is the true method of science (and learning generally), in contrast to the empiricist and inductivist view that knowledge begins with observation, and ends up being verified or warranted by reference to sense impressions.
"This, I believe, is the true theory of knowledge (which I wish to submit to your criticism): the true description of a practice which arose in Ionia and which is incorporated in modern science (though there are many scientists who still believe in the Baconian myth of induction): the theory that knowledge proceeds by way of conjectures and refutations."