6. The result of such controversies as we have been speaking of, often appears to be summed up in a _Definition_; and the controversy itself has often assumed the form of a battle of definitions. For example, the inquiry concerning the Laws of Falling Bodies led to the question whether the proper Definition of a _uniform force_ is, that it generates a velocity proportional to the _space_ from rest, or to the _time_. The controversy of the _Vis Viva_ was, what was the {36} proper Definition of the _measure of force_. A principal question in the classification of minerals is, what is the Definition of a _mineral species_. Physiologists have endeavoured to throw light on their subject, by Defining _organization_, or some similar term. 7. It is very important for us to observe, that these controversies have never been questions of insulated and _arbitrary_ Definitions, as men seem often tempted to suppose them to have been. In all cases there is a tacit assumption of some Proposition which is to be expressed by means of the Definition, and which gives it its importance. The dispute concerning 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 presumed that 'individuals so related resemble each other more than those which are excluded by such a definition;' or perhaps, that 'species so defined have permanent and definite differences.' A definition of Organization, or of any 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 Conceptions; 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 Conception shall be understood and defined in order that the Proposition may be true.