Reprinted from ‘Critica Revista Hispanoamericana de Filosfía’, vol. , by permission of the editors of that journal; originally delivered as a lecture in July 1965 to the Summer School at

the University of Edinburgh

If we are asked to give a list of the ten most influential philosophers of all time, we are likely to have the name ‘John Locke’ in our list, even, perhaps, fairly high in the list. It is not much of an exaggeration to say that one cannot pick up a sermon, a novel, pamphlet or a treatise and be in any doubt, after reading a few lines, whether it was written before or after the publication of Locke’s Essay concerning Human Understanding, which was in 1690. The intellectual atmosphere since Locke has had quite a different smell from what it had before Locke. If we could fly back in a time-rocket to England in 1700, we could already breathe its air, and we could already converse with our new acquaintances there without feeling lost. In the England of, say, 1600, we should gasp like fishes out of water. But if we are then asked what Locke’s great contribution was, we find it very difficult to answer.