A race preserves its vigour so long as it harbours a real contrast between what has been and what may be; and so long as it is nerved by the vigour to adventure beyond the safeties of the past. Without adventure civilization is in full decay.

It is for this reason that the definition of culture as the knowledge of the best that has been said and done, is so dangerous by reason of its omission. It omits the great fact that in their day the great achievements of the past were the adventures of the past. Only the adventurous can understand the greatness of the past. In its day, the literature of the past was an adventure. Aeschylus, Sophocles, Euripides were adveturers in the world of thought. To read their plays without any sense of new ways of understanding the world and of savouring its emotions is to miss the vividness which constitutes their whole value. But adventures are to the adventurous. Thus a passive knowledge of the past loses the whole value of its message. A living civilization requires learning; but it lies beyond it.

- Whitehead, Adventures of Ideas, "Adventure," Section III, p. 360.