But in the course of its discussion an important difference has been brought to light between external and internal purposes or ends. The kind of design in nature which first arrested early thinkers was its usefulness to man. Even in scenery, it has been suggested, they saw the utility before the beauty. And so they came to look upon all natural phenomena as having for their final cause the good of man; and the world as a machine, a contrivance of which the parts have no value except as contributing to the work of the whole, and the whole exists only to produce a result outside and independent of itself, an external end, as if corn should exist solely to provide food for man. This was not an untrue conception; a shallow thing to say of the reason for which Socrates believed in God; but it was partial and inadequate, as Bacon and Spinoza shewed. And we have now come to regard the world not as a machine, but as an organism, a system in which, while the parts contribute to the growth of the whole, the whole also reacts upon the development of the parts; and whose primary purpose is its own perfection, something that is contained within and not outside itself, an internal end: while in their turn the myriad parts of this universal organism are also lesser organisms, ends in and for themselves, pursuing each its lonely ideal of individual completeness. Now when we look at nature in this way, and watch the complex and subtle processes by which a crystal, a leaf, a lily, a moth, a bird, a star realize their respective ideals with undisturbed, unfailing accuracy, we cannot help attributing them to an intelligent Creator. But when we further find that in the very course of pursuing their primary ends, and becoming perfect after their kind, the various parts of the universe do in fact also become means, and with infinite ingenuity of correspondence and adaptation, subserve not only one but a thousand secondary ends, linking and weaving themselves together by their mutual ministration into an orderly, harmonious, complicated whole, the signs of intelligence grow clearer still. And when, beyond all this, we discover the quality of beauty in every moment and situation of this complex life; the drop of water that circulates from sea to cloud, and cloud to earth, and earth to plant, and plant to life-blood, shining the while with strange spiritual significance in the sunset and the rainbow and the dewdrop and the tear; the universal presence of this attribute, so unessential to the course of nature, but so infinitely powerful in its appeal to the human mind, is reasonably urged as a crowning proof of purposeful design.