But, secondly, there is another obvious question to which an answer is necessary. Mr. Kidd and Mr. Galton deduce their view about Greek intellect, first, from the proportion of great men. Does, then, the occurrence of a group of great men at a certain period prove a superior organisation in the race? That leads to a very familiar problem: What were the causes of what we may call the flowering times of arts and sciences? We are all familiar with the phenomenon; with the sudden display of astonishing excellence at Athens, at Florence, or in the England of Elizabeth. It seems to be the rule that processes which may have been going on quietly for centuries suddenly culminate; that artistic, poetic, or philosophic excellence becomes unprecedentedly common for a generation or two, and that the impulse then dies away as rapidly. It is the kind of problem which is satisfactorily solved by the authors of university prize essays, which somehow fail to convince the world or to be republished by their writers. Are we, then, entitled to argue from the great works an organic superiority in the race? Must we suppose, for example, that Englishmen at the time of Shakespeare and Bacon and Spenser and Raleigh were an abler race than their descendants, because, when there was a very much smaller number of educated men, they produced more first-rate authors than have been produced by generations much more numerous and more generally cultivated? This seems to me at least to be a very rash hypothesis; and some of the obvious remarks made in our university essays seem to me to indicate considerations which, though not conclusive, cannot be neglected. It is clear, for example, that particular stages of intellectual progress are abnormally stimulating; that, as the last step to a pass in the mountains suddenly reveals vast prospects, while a hundred equally difficult steps before made no appreciable change, so there are mental advances which, as at the time of Bacon, seemed suddenly to disclose boundless prospects of knowledge. It is the Pisgah sight of the promised land which causes a burst of energy. Or, again, a certain social condition is obviously required; philosophers and poets may exist potentially among barbarous tribes, but they cannot get a chance to speak, and they have no opportunity of communication with other thinkers. The intellect may be impelled in various directions, some of which leave no trace of a tangible kind. The amount of intellectual power implied in building up the Roman Empire may have been as great as that implied in developing Greek art; and in America, as we are often told, intellect turns to dollar-making, instead of book-writing. So, conversely, the outburst of power may indicate, not greater faculties, but special opportunities, or special stimulus, applied to already existing faculties. Everybody who has written an æsthetic treatise has pointed to all manner of conditions which were in this sense favourable to the Greeks.