From "Newton, the Man," a lecture prepared by John Maynard Keynes and delivered by his brother, Geoffrey, in July 1946:
In the Eighteenth century and since, Newton came to be thought of as the first and greatest of the modern age of scientists, a rationalist, one who taught us to think on the lines of cold and untinctured reason.From "On a Method of Statistical Business-Cycle Research. A Comment" J. M. Keynes. The Economic Journal, Vol. 50, No. 197. (Mar., 1940), pp. 154-156:
I do not see him in this light. I do not think that any one who has pored over the contents of that box which he packed up when he finally left Cambridge in 1696 and which, though partly dispersed, have come down to us, can see him like that. Newton was not the first of the age of reason. He was the last of the magicians, the last of the Babylonians and Sumerians, the last great mind which looked out on the visible and intellectual world with the same eyes as those who began to build our intellectual inheritance rather less than 10,000 years ago. Isaac Newton, a posthumous child born with no father on Christmas Day, 1642, was the last wonderchild to whom the Magi could do sincere and appropriate homage. ...
A large section [of Newton's papers], judging by the handwriting amongst the earliest, relates to alchemy - transmutation, the philosopher's stone, the elixir of life. The scope and character of these papers have been hushed up, or at least minimized, by nearly all those who have inspected them. About 1650 there was a considerable group in London, round the publisher Cooper, who during the next twenty years revived interest not only in the English alchemists of the fifteenth century, but also in translations of the medieval and post-medieval alchemists.
There is an unusual number of manuscripts of the early English alchemists in the libraries of Cambridge. It may be that there was some continuous esoteric tradition within the University which sprang into activity again in the twenty years from 1650 to 1670. At any rate, Newton was clearly an unbridled addict. It is this with which he was occupied 'about 6 weeks at spring and 6 at the fall when the fire in the elaboratory scarcely went out' at the very years when he was composing the Principia - and about this he told Humphrey Newton not a word.
No one could be more frank, more painstaking, more free from subjective bias or parti pris than Professor Tinbergen. There is no one, therefore, so far as human qualities go, whom it would be safer to trust with black magic. That there is anyone I would trust with it at the present stage, or that this brand of statistical alchemy is ripe to become a branch of science, I am not yet persuaded. But Newton, Boyle and Locke all played with Alchemy. So let him continue.
See also: My Dinner with Maynard.
Keynes on econometric method. A reassessment of his debate with Tinbergen and other econometricians, 1938-1943. Giovanna Garrone e Roberto Marchionatti. CESMEP Working Paper. 2004.
Hendry, D.F. (1980). "Econometrics - Alchemy or Science?" Economica, 47, August, 387-406.