"I shall instance the history of science, which I divide into two periods, one ending in 1800, the other coming down to the present. Until the time of Volta, scientific research and speculation had from the beginning been practiced on identical phenomena. For example, no one had yet observed or even imagined that mechanical or chemical effects, or eifects of light or heat, could occur along the length of an oddly twisted wire. In any case, the very idea then held of science implicitly excluded the possibility of absolutely unpredictable facts.
"In that state of knowledge one could speak of the universe and the unity of nature without doubting that one knew what one was saying. There were such things as time, space, matter, light, and a quite precise distinction between the inorganic world and the other; and the expression to know everything, which is the complement of the word universe, seemed to have a meaning and to be a perfectly clear delimiting expression. Laplace was able to imagine a mind powerful enough to embrace, or to deduce from a finite number of observations, all possible phenomena past and to come.
"But once an electric current was set going, the era of entirely new facts began. Each new fact was in its own way an attack on the theoretical structure of universal dynamics, which was thought to have been conceived in the widest possible generality. The very notion of physical theory has in the end been seriously, if not definitively, compromised. First of all, the mental imagery that had done such good service lost all its meaning once speculation was concerned no longer with subphenomena assumed to be similar to the phenomena directly observed, but rather with "things" that in no way resemble the things we know, since they only send us signals which we interpret as best we can. Furthermore, our language, and hence our logic, our concepts, our causality, our principles, have been found wanting: all this intellectual material will not fit into the nucleus of the atom, where everything is without precedent and without shape. Debatable probabilities have taken the place of definite and distinct facts, and the fundamental distinction between observation and its object is no longer conceivable.
"What has happened? Simply that our means of investigation and action have far outstripped our means of representation and understanding."
- Paul Valéry, "Unpredictability" , published in The Outlook for Intelligence, translated into English by Denise Folliot and Jackson Matthews