The doctrine of final causes is generally regarded as a constituent principle of religious systems. A special argument in favour of the existence of God has even been drawn from it. Comte remarks that it is more probably a consequence of these systems. So long as man believes in the continual action of the gods, or of God, in nature, he does not need the consideration of final causes upon which to found his belief. He does not even dream of it. Later on only, when the religious conception of the world has become weaker, when God has so far withdrawn from the world as to be no longer anything but a sovereign who reigns, but does not govern, then the need is felt to demonstrate His existence, and the order of nature becomes an argument. The consideration of final causes from this point of view is a symptom of the weakening of the theological spirit; it is thus pre-eminently a metaphysical doctrine. Whatever may be the case, experience witnesses against it. Positive science does not lay down that the world must be conceived as the work of an all-powerful intelligence. For instance, the scientific knowledge of our solar system has shown in the most obvious manner, and in various ways, that the elements of this system were certainly not disposed in the most advantageous manner, and that science allowed us to conceive of a better arrangement.[55] Astronomers may admire a natural finality in the organisation of animals; but the anatomists who know all its imperfections, fall back upon the arrangements of the stars. In what concerns animals, a blind admiration wonders even at evidently detrimental complications: it is the case with the eye, with the bladder, etc.[56] But “it is an almost universal disposition of physiologists to draw, even from their ignorance, as many motives for the admiration of the profound wisdom of a mechanism which they declare they cannot understand.”