[85] Ibid. ii. 653.
[86] Miller’s Chemistry, ii. p. 654.
I will, in the last place, propound an Aphorism which has already offered itself in considering the history of Chemistry[87] as having a special bearing upon that Science, but which may be regarded as the supreme and ultimate rule with regard to the language of Science.
[87] Hist. Ind. Sc. b. xiv. c. 1.
Aphorism XXIX.
In learning the meaning of Scientific Terms, the history of science is our Dictionary: the steps of scientific induction are our Definitions.
It is usual for unscientific readers to complain that the technical terms which they meet with in books of science are not accompanied by plain definitions such as they can understand. But such definitions cannot be given. For definitions must consist of words; and, in the case of scientific terms, must consist of words which require again to be defined: and so on, without limit. Elementary substances in chemistry, for instance, what are they? The substances into which bodies can be analysed, and by the junction of which they are composed. But what is analysis? what is composition? We have seen that it required long and laborious courses of experiment to answer these questions; and that finally the balance decided among rival answers. And so it is in other cases. In entering upon each science, we come upon a new set of words. And how are we to learn 369 the meaning of this collection of words? In what other language shall it be explained? In what terms shall we define these new expressions? To this we are compelled to reply, that we cannot translate these terms into any ordinary or familiar language. Here, as in all other branches of knowledge, the meaning of words is to be sought in the progress of thought. It is only by going back through the successful researches of men respecting the composition and elements of bodies, that we can learn in what sense such terms can be understood, so as to convey real knowledge. In order that they may have a meaning for us, we must inquire what meaning they had in the minds of the authors of our discoveries. And the same is the case in other subjects. To take the instance of Morphology. When the beginner is told that every group of animals may be reduced to an Archetype, he will seek for a definition of Archetype. Such a definition has been offered, to this effect: the Archetype of a group of animals is a diagram embodying all the organs and parts which are found in the group in such a relative position as they would have had if none had attained an excessive development. But, then, we are led further to ask, How are we in each case to become acquainted with the diagram; to know of what parts it consists, and how they are related; and further; What is the standard of excess? It is by a wide examination of particular species, and by several successive generalizations of observed facts, that we are led to a diagram of an animal form of a certain kind, (for example, a vertebrate;) and of the various ways, excessive and defective, in which the parts may be developed.
This craving for definitions, as we have already said, arises in a great degree from the acquaintance with geometry which most persons acquire at an early age. The definitions of geometry are easily intelligible by a beginner, because the idea of space, of which they are modifications, is clearly possessed without any special culture. But this is not and cannot be the case in other sciences founded upon a wide and exact observation of facts. 370
It was formerly said that there was no Royal Road to Geometry: in modern times we have occasion often to repeat that there is no Popular Road—no road easy, pleasant, offering no difficulty and demanding no toil,—to Comparative Anatomy, Chemistry or any other of the Inductive Sciences.
THE END.