When final cause is employed to signify design in any reference, be it to intrinsic, extrinsic, or ultimate ends, I have nothing to object to Bacon and Descartes's condemnation of it as illegitimate and unprofitable in science. I know of no science, physical or moral, in which, while thus understood, it can be of the slightest use as a principle of scientific discovery. It is as much out of place in the world of organic as of inorganic nature. It is quite incorrect to say that although it does not lead to the discovery of new truths in strictly physical science, it does so in physiology for example, or in psychology, or in ethics. It is only when it means merely the inherent order and adjustment of things--not when it means designs and purposes regarding them--that the search after it can possibly lead to scientific truth, and, when so understood, it leads to truth in all sciences alike. It was the suggestive principle in Adams and Leverrier's discovery of the planet Neptune from certain unexplained perturbations of the planet Uranus, quite as much as in Harvey's discovery of the circulation of the blood from the observation of certain unexplained valves at the outlet of the veins and the rise of the arteries. It is involved in the very nature of the inductive process, and is only confirmed and enlarged by the progress of inductive research. It stands in no opposition to the principle of efficient causes, and is in no degree disproved by the discovery of such causes. Assertions to the effect that it has gradually been driven by the advance of knowledge from the simpler sciences into those which are complex and difficult,--that it is being expelled even out of biology and sociology--and that it always draws its confirmation, not from phenomena which have been explained, but from phenomena which await explanation,--are often made, but they rest almost exclusively on the wishes of those who make them. They have no real historical basis.[29] [29] See Appendix XXI. LECTURE VI. OBJECTIONS TO THE ARGUMENT FROM ORDER EXAMINED. I.