Astronomers tell us that in all likelihood the earth will remain habitable for very many millions of years. Man has existed for about a million years. Therefore if all goes well his future should be immeasurably longer than his past. Broadly speaking, we are in the middle of a race between human skill as means and human folly as to ends. Given sufficient folly as to ends, every increase in the skill required to achieve them is to the bad. The human race has survived hitherto owing to ignorance and incompetence; but, given knowledge and incompetence combined with folly, there can be no certainty of survival. Knowledge is power, but it is power for evil just as much as for good. It follows that, unless men increase in wisdom as much as in knowledge, increase of knowledge will be increase of sorrow.