REQUISITES OF LANGUAGE. 221 



principal question in the classification of minerals is, what is 

 the definition of a, mineral species. Physiologists have endea- 

 voured to throw light on their subject hy defining organiza- 

 tion, or some similar term." Questions of the same nature 

 are still open respecting the definitions of Specific Heat ? 

 Latent Heat, Chemical Combination, and Solution. 



" It is very important for us to observe, that these con- 

 troversies have never been questions of insulated and arbitrary 

 definitions, as men seem often tempted to imagine them to 

 have been. In all cases there is a tacit assumption of some 

 proposition which is to be expressed by means of the defini- 

 tion, and which gives it its importance. The dispute con- 

 cerning the definition thus acquires a real value, and becomes 

 a question concerning true and false. Thus in the discussion 

 of the question, What is a uniform force ? it was taken for 

 granted that gravity is a uniform force. In the debate of the 

 vis viva, it was assumed that in the mutual action of bodies 

 the whole effect of the force is unchanged. In the zoological 

 definition of species, (that it consists of individuals which 

 have, or may have, sprung from the same parents,) it is pre- 

 sumed that individuals so related resemble each other more 

 than those which are excluded by such a definition ; or, per- 

 haps, that species so defined have permanent and definite 

 differences. A definition of organization, or of some other 

 term, which was not employed to express some principle, 

 would be of no value. 



" The establishment, therefore, of a right definition of a 

 term, may be a useful step in the explication of our concep- 

 tions ; but this will be the case then only when we have 

 under our consideration some proposition in which the term is 

 employed. For then the question really is, how the concep- 

 tion shall be understood and defined in order that the proposi- 

 tion may be true. 



" To unfold our conceptions by means of definitipns has 

 never been serviceable to science, except when it has been 

 associated with an immediate use of the definitions. The 

 endeavour to define a Uniform Force was combined with the 

 assertion that gravity is a uniform force : the attempt to 



