Nor will such study ever be irksome to him whose generous desire after knowledge, is thus deservedly gratified.
10.

But it must be understood, that although scientific definitions are said to be _of things_, they are not copied immediately from the real essence of the things, but are formed from the conceptions of the author's mind concerning that essence.

Hence, as Duncan justly remarks, "A mistaken idea never fails to occasion a mistake also in the definition." Hence, too, the common distinction of the logicians, between definitions of the _name_ and definitions of the _thing_, seems to have little or no foundation.

The former term they applied to those definitions which describe the objects of pure intellection, such as triangles, and other geometrical figures; the latter, to those which define objects actually existing in external nature.
The mathematical definitions, so noted for their certainty and completeness, have been supposed to have some peculiar preeminence, as belonging to the former class.

But, in fact the idea of a triangle exists as substantively in the mind, as that of a tree, if not indeed more so; and if I define these two objects, my description will, in either case, be equally a definition both of the name and of the thing; but in neither, is it copied from any thing else than that notion which I have conceived, of the common properties of all triangles or of all trees.
11.