Dissertation, Oxford, Tercentenary John Locke Conference (April 2-4, 2004) (2004
Widespread amongst scholars is the legend according to which Locke shows a strong aversion to abstract ideas, similar to that of Berkley in the Treatise. This legend is endorsed by influential commentators on Locke. He does not even propose the reduction of ideas to mental pictures (a reduction which in Berkeley and Hume will form the base of the negation of the existence of abstract ideas in the mind). Locke is not in the least afraid of abstract ideas; his constant concern, which is evident in his treatment of the complex question of the relation between real and nominal essence, is to refute the position of the Scholastics, according to which a universal concept in the mind (post rem) reflects the universal present in all things as substantial form (the universal in re), without assuming positions which are purely conventionalist and nominalist with regard to knowledge, such as those of Mersenne, Gassendi, Hobbes and sceptical and anti-Cartesian free-thinkers. To show this, I offer an analysis of the relation Locke makes between real and nominal essence, with regard to the relations which link term to idea and idea to things. The nature of the relation between signifier and signified is variable, though, in the relation between ideas and things with respect to the various kinds of complex ideas which the human mind may frame. The greatest difference is to be found between complex ideas of mixed mode and complex ideas of substance.