“His [Darwin's] work on the ‘Origin of Species’ does not purport to be philosophical. In this aspect it is very different from the cognate works of Mr. Spencer. Darwin does not speculate on the origin of the universe, on the nature of matter or of force. He is simply a naturalist, a careful and laborious observer, skillful in his descriptions, and singularly candid in dealing with the difficulties in the way of his peculiar doctrine. He set before himself a single problem—namely, How are the fauna and flora of our earth to be accounted for? … To account for the existence of matter and life, Mr. Darwin admits a Creator. This is done explicitly and repeatedly. … He assumes the efficiency of physical causes, showing no disposition to resolve them into mind-force or into the efficiency of the First Cause. … He assumes, also, the existence of life in the form of one or more primordial germs. […]