_When common words are appropriated as technical terms, this must be done so that they are not ambiguous in their application._ AN example will explain this maxim. The conditions of a body, as a solid, a liquid, and an air, have been distinguished as different _forms_ of the body. But the word _form_, as applied to bodies, has other meanings; so that if we were to inquire in _what form_ water exists in a snow-cloud, it might be doubted whether the forms of crystallization were meant, or {282} the different forms of ice, water, and vapour. Hence I have proposed[23\4] to reject the term _form_ in such cases, and to speak of the different _consistence_ of a body in these conditions. The term _consistence_ is usually applied to conditions between solid and fluid; and may without effort be extended to those limiting conditions. And though it may appear more harsh to extend the term _consistence_ to the state of air, it may be justified by what has been said in speaking of Aphorism V. [Note 23\4: _Hist. Ind. Sc._ b. x. c. ii. sect. 2.] I may notice another example of the necessity of avoiding ambiguous words. A philosopher who makes method his study, would naturally be termed a _methodist_; but unluckily this word is already appropriated to a religious sect: and hence we could hardly venture to speak of Cæsalpinus, Ray, Morison, Rivinus, Tournefort, Linnæus, and their successors, as _botanical methodists_. Again, by this maxim, we are almost debarred from using the term _physician_ for a cultivator of the science of physics, because it already signifies a practiser of physic. We might, perhaps, still use _physician_ as the equivalent of the French _physicien_, in virtue of Aphorism V.; but probably it would be better to form a new word. Thus we may say, that while the Naturalist employs principally the ideas of resemblance and life, the _Physicist_ proceeds upon the ideas of force, matter, and the properties of matter. Whatever may be thought of this proposal, the maxim which it implies is frequently useful. It is this. APHORISM VII. _It is better to form new words as technical terms, than to employ old ones in which the last three Aphorisms cannot be complied with._ THE principal inconvenience attending the employment of new words constructed expressly for the use of science, is the difficulty of effectually introducing them. Readers will not readily take the trouble to learn the meaning of a word, in which the memory is {283} not assisted by some obvious suggestion connected with the common use of language. When this difficulty is overcome, the new word is better than one merely appropriated; since it is more secure from vagueness and confusion. And in cases where the inconveniences belonging to a scientific use of common words become great and inevitable, a new word must be framed and introduced.