PROPAGANDA NOT SCIENCE.--It is very doubtful whether the genuine scientists, who devoted themselves not to propaganda but to research, could have been ready to sanction the uses to which their own discoveries were put. From the exhaustive references of Lange in his _History of Materialism_ (Engl. Trans., Vol. II, pp. 49-123), it is evident that "the extreme views of La Mettrie, Diderot, and Holbach cannot be fathered on any of the great scientists or philosophers, but were an attempt to supply scientific principles to the solution of philosophical, ethical, or religious questions, frequently for practical and political purposes."[21] There are certainly risks attached to the popularisation of the results of scientific research. Theories have to be presented with an appearance of finality which does not legitimately belong to them, and sometimes in a somewhat startling aspect, otherwise the reader is left cold, for it is excitement rather than genuine information that attracts the majority. As a judicious writer has observed: "No ideas lend themselves to such easy, but likewise to such shallow generalisations as those of science. Once let out of the hand which uses them in the strict and cautious manner by which alone they lead to valuable results, they are apt to work mischief. Because the tool is so sharp, the object to which it is applied seems to be so easily handled. The correct use of scientific ideas is only learnt by patient training, and should be governed by the not easily acquired habit of self-restraint."[22] SCIENTIFIC PROGRESS.--Alongside of this rigorous propaganda, which prepared the way for the upheaval of 1789, genuine scientific progress was being made, especially in the regions of Astronomy, Botany and Chemistry. The ideas of Newton were taken up and elaborated by means of more efficient mathematical processes--especially the theory of infinitesimals--by the distinguished astronomer, Laplace, in his _Systeme du Monde_ (1796), and in the successive volumes of his _Mechanique Celeste_ (1799-1825), which has been called a new _Principia_.