Then we might consider the existence of the roof. In short, we would soon find ourselves involved in a mesh of cause and effect, from which we would soon strive to extricate ourselves.
Just as a man has two parents, and four grandparents, and eight great-grandparents, and sixteen great-great-grandparents, and so on until when, say, forty generations are calculated the numbers of ancestors run into many millions—so it is with the number of causes behind even the most trifling event or phenomena, such as the passage of a tiny speck of soot before your eye. It is not an easy matter to trace the bit of soot back to the early period of the world's history when it formed a part of a massive tree-trunk, which was afterward converted into coal, and so on, until as the speck of soot it now passes before your vision on its way to other adventures. And a mighty chain of events, causes and effects, brought it to its present condition, and the latter is but one of the chain of events which will go to produce other