Tuesday, January 1, 2019

"You Cannot Convict Your Opponent of Error; You Can Only Convince Him Of It"

Those of us who write about economics can only nod knowingly at a comment from John Maynard Keynes in 1934, in a a fragment of writing that was probably part of a draft of the preface for the General Theory. He wrote:
"[A]n economic writer requires from his reader much goodwill and intelligence and a large measure of co-operation ... In economics you cannot convict your opponent of error; you can only convince him of it." 
Happy New Year. And thanks to all the regular, semi-regular, occasional, and one-time readers for your goodwill, intelligence, cooperation--and for taking a look at this blog now and then. I published this same quotation a year ago on New Year's Day, but it still echoed in my mind this year.

The quotation from Keynes appears in volume XIII of the Collected Works of John Maynard Keynes, edited by Donald Moggridge and published in 1973 (pp. 469-471). Here's a fuller quotation from the passage, both worth reading for itself, and also to give some context:
When we write economic theory, we write in a quasi-formal style; and there can be no doubt, in spite of the disadvantages, that this is our best available means of conveying our thoughts to one another. But when an economist writes in a quasi-formal style, he is composing neither a document verbally complete and exact so as to be capable of a strict legal interpretation, nor a logically complete proof. Whilst it is his duty to make his premises and his use of terms as clear as he can, he never states all his premises and his definitions are not perfectly clear-cut. He never mentions all the qualifications necessary to his conclusions. He has no means of stating, once and for all, the precise level of abstraction on which he is moving, and he does not move on the same level all the time. It is, I think, of the essential nature of economic exposition that it gives, not a complete statement, which, even if it were possible, would be prolix and complicated to the point of obscurity but a sample statement, so to speak, out of all the things which could be said, intended to suggest to the reader the whole bundle of associated ideas, so that, if he catches the bundle, he will not in the least be confused or impeded by the technical incompleteness of the mere words which the author has written down, taken by themselves. 
This means, on the one hand, that an economic writer requires from his reader much goodwill and intelligence and a large measure of co-operation; and, on the other hand, that there are a thousand futile, yet verbally legitimate, objections which an objector can raise. In economics you cannot convict your opponent of error; you can only convince him of it. And, even if you are right, you cannot convince him, if there is a defect in your own powers of persuasion and exposition or if his head is already so filled with contrary notions that he cannot catch the clues to your thought which are trying to throw to him. 
The results is that much criticism, which has verbal justification in what the author has written, is nevertheless altogether futile and maddeningly irritating; for it merely indicates that the minds of authors and reader have failed to meet. ....
I ask forgiveness, therefore, if I have failed in the necessary goodwill and intellectual sympathy when I criticise; and to those minds to which, for whatever reasons, my ideas do not find an easy entry, I offer the assurance in advance that they will not find it difficult, where the country to be traversed is so extensive and complicated, to discover reasons which will seem to them adequate, for refusing to follow. Time rather than controversy ... will sort out the true from the false.