Now here we have in another form that same vicious tendency to take refuge in the more obscure cases of physical causation as proofs of supernatural design--the obscurity in this case arising from the _complexity_ of the causes and work, as in the former case it arose from their _remoteness_ in time. But in both cases the same answer is patent, viz., that although "physical science cannot answer these questions" by pointing out the precise sequence of causes and effects, physical science is nevertheless quite as certain that this precise sequence arises in its last resort from the persistence of force, as she would be were she able to trace the whole process. And therefore, in view of the considerations set forth in Chapter IV. of this work, it is no longer open to Professor Flint or to any other writer logically to assert--"I can conceive of no other intelligent answer being given to" such questions "than that there is a God of wisdom." The same answer awaits this author's further disquisition on other biological laws, so it is needless to make any further quotations in this connection. But there is one other principle embodied in some of these passages which it seems undesirable to overlook. It is said, for instance, "Natural selection might have had no materials, or altogether insufficient materials, to work with, or the circumstances might have been such that the lowest organisms were the best endowed for the struggle for life. If the earth were covered with water, fish would survive and higher creatures would perish."