As Cuvier could correctly describe a whole animal by the contemplation of a single bone, so the observer who has thoroughly understood one link in a series of incidents should be able to accurately state all the other ones, both before and after.
My sister and I, you will recollect, were twins, and you know how subtle are the links which bind two souls which are so closely allied.
So all life is a great chain, the nature of which is known whenever we are shown a link of it.