Between forty and fifty years ago a great European man of science, Emil du Bois-Reymond, delivered before an audience of the leading scientific men of Germany a famous discourse on The Limits of our Knowledge of Nature, which he followed up some years later with a second discourse on the Seven Riddles of the Universe.  His object was to convince the materialists of the ’seventies that there were at least seven such unsound places in their story of everything.  Some of the ‘riddles’, he admitted, might prove to be soluble as science advances, but the most important of them will always remain unanswered.  Our position as regards them will always be ignoramus et ignorabimus—­we do not know the solutions and we never shall know them.  I do not ask now whether du Bois-Reymond was right in his judgement or not.  If he was right, that means, of course, that the one tale of everything will never be told by human lips to human ears.  There will no more ever be a finally true Philosophy than there will ever be a finally perfect poem or picture or symphony.  But there is no reason why we should not, at any rate, try to make our story as nearly perfect as we can, to reduce the number of the places where we have to break off with ‘that is another story’, and perhaps even to hazard a ‘wide solution’ in matters where absolute certainty is beyond our reach.  This is the work of human Philosophy as I conceive it, and every man who is disinterestedly trying, without one eye on wealth or fame or domination over the minds of others, to make any contribution, however humble, to the telling of this one story or the removal of loose threads from it, is inspired by the true spirit of Philosophy.  Whoever is doing anything else, no matter under what name or with what profit or renown to himself, is no true philosopher.

This point of view implies, it will be seen, no sharp dividing line between Philosophy and Science.  The avoidance of this commonly made distinction may offend two different sets of students—­students of metaphysics who wish to exalt their own pursuit at the expense of the ‘special’ sciences, and students of natural science who are accustomed to pride themselves on the contrast between the finality and definiteness of their own results and the vagueness and dubiousness of the conclusion of the metaphysicians.  But I must avow my own conviction that the only distinction we can make is one of convenience, and it may help to make my peace with both parties if I explain where I take this distinction of convenience to come in.  If we are ever to construct an approximation to the one story of everything, clearly one result will consist of a relatively few first principles and a great mass of conclusions which can be inferred from them.  And clearly again, since men differ so widely in their mental aptitudes, some men will be most successful in the detection of the principles which underlie all our knowledge, and others most successful in the accumulation