In uncharacteristically bold discussions after dinner Darwin asked his guests "Why do you call yourselves Atheists?" When they responded that they "did not commit the folly of god-denial, [and] avoided with equal care the folly of god-assertion", Darwin gave a thoughtful response, concluding that "I am with you in thought, but I should prefer the word Agnostic to the word Atheist." Aveling replied that, "after all, 'Agnostic' was but 'Atheist' writ respectable, and 'Atheist' was only 'Agnostic' writ aggressive." Darwin smiled and responded "Why should you be so aggressive? Is anything gained by trying to force these new ideas upon the mass of mankind? It is all very well for educated, cultured, thoughtful people; but are the masses yet ripe for it?" Aveling and Büchner questioned what would have happened if Darwin had been given that advice before publication of the Origin, and had confined "the revolutionary truths of Natural and Sexual Selection to the judicious few", where would the world be? Many feared danger if new ideas were "proclaimed abroad on the house-tops, and discussed in market-place and home. But he, happily for humanity, had by the gentle, irresistible power of reason, forced his new ideas upon the mass of the people. And the masses had been found ripe for it. Had he kept silence, the tremendous strides taken by human thought during the last twenty-one years would have been shorn of their fair proportions, perhaps had hardly been made at all. His own illustrious example was encouragement, was for a command to every thinker to make known to all his fellows that which he believed to be the truth."
Their talk turned to religion, and Darwin said ""I never gave up Christianity until I was forty years of age." He agreed that Christianity was "not supported by the evidence", but he had reached this conclusion only slowly. Aveling recorded this discussion, and published it in 1883 as a penny pamphlet. Francis Darwin thought it gave "quite fairly his impressions of my father's views, but took issue with any suggestion of similar religious views, saying "My father's replies implied his preference for the unaggressive attitude of an Agnostic. Dr. Aveling seems to regard the absence of aggressiveness in my father's views as distinguishing them in an unessential manner from his own. But, in my judgment, it is precisely differences of this kind which distinguish him so completely from the class of thinkers to which Dr. Aveling belongs." Wikipedia
Good point! The better the man is understood, the better to understand what he wrote.