"Well, suppose we say——the last of a series of connected events——each of the series being the cause of the next——for whose sake the first event takes place."
"But the last event is practically an effect of the first, isn't it? And yet you call it a cause of it!"
Arthur pondered a moment. "The words are rather confusing, I grant you," he said. "Will this do? The last event is an effect of the first: but the necessity for that event is a cause of the necessity for the first."
"That seems clear enough," said Lady Muriel. "Now let us have the problem."
"It's merely this. What object can we imagine in the arrangement by which each different size (roughly speaking) of living creatures has its special shape? For instance, the human race has one kind of shape——bipeds. Another set, ranging from the lion to the mouse, are quadrupeds. Go down a step or two further, and you come to insects with six legs——hexapods——a beautiful name, is it not? But beauty, in our sense of the word, seems to diminish as we go down: the creature becomes
