Speaking exclusively of observational and experimental sciences, it is obvious that progress can be accomplished only at the cost of destroying or modifying current theories; for if a theory suffices to explain facts discovered after its promulgation, knowledge may be increased; but there is no true progress unless our general outlook is altered.
Men who are capable of modifying their first beliefs are very rare. This ability was one of the reasons for the success of Claude Bernard and Pasteur. Out of a very vivid imagination they forged new hypotheses all the time but abandoned them with equal ease as soon as experience contradicted them.
The number of known metals had been increased by one — from 17 to 18.... A few years ago we thrilled to hear of the discovery of the final planet by Sir William Herschel. He calls the new member of our solar system Uranus. I propose to borrow from the honor of that great discovery and call this new element Uranium.
The end of chemistry is its theory. The guide in chemical research is a theory. It is therefore of the greatest importance to ascertain whether the theories at present adopted by chemists are adequate to the explanation of chemical phenomena, or are at least based upon the true principles which ought to regulate scientific research.
Scientists know that research merely discloses parts of the infinite unknown. Paradoxically, the enticing, helpful "unknown" increases as men continue to subtract from it. Progress in every line of experimental science follows the same law. The apparently narrow path gradually expands into unlimited, unexplored territory.
Chemistry is not yet a science. We are very far from the knowledge of first principles. We should avoid every thing that has the pretensions of a full system. The whole of chemical science should, as yet, be analytical, like Newton's Optics, in the form of a general law, at the very end of our induction, as the reward of our labour.
There is not a "pure" science. By this I mean that physics impinges on astronomy, on the one hand, and chemistry and biology on the other. And not only does each support neighbors, but derives sustenance from them. The same can be said of chemistry. Biology is, perhaps, the example par excellence today of an "impure" Science.