book) with the accuracy of single ideas, and advancing (in Book iv., which
is the most important in the whole work) to the truth of judgments. An idea
is real when it conforms to its archetype, whether this is a thing, real
or possible, or an idea of some other thing; it is adequate when the
conformity is complete. The idea of a four-sided triangle or of brave
cowardice is unreal or fantastical, since it is composed of incompatible
elements, and the idea of a centaur, since it unites simple ideas in a
way in which they do not occur in nature. The layman's ideas of law or of
chemical substances are real, but inadequate, since they have a general
resemblance to those of experts, and a basis in reality, but yet only
imperfectly represent their archetypes. Nay, further, our ideas of
substances are all inadequate, not only when they are taken for
representations of the inner essences of things (since we do not know these
essences), but also when they are considered merely as collections of
qualities. The copy never includes all the qualities of the thing, the less
so since the majority of these are powers, _i.e._, consist in relations to
other objects, and since it is impossible, even in the case of a single
body, to discover all the changes which it is fitted to impart to, or
to receive from, other substances. Ideas of modes and relations are all
adequate, for they are their own archetypes, are not intended to represent
anything other than themselves, are images without originals. An idea of
this kind, however, though perfect when originally formed, may become
imperfect through the use of language, when it is unsuccessfully intended
to agree with the idea of some other person and denominated by a current
term. In the case of mixed modes and their names, therefore, the
compatibility of their elements and the possible existence of their objects
are not enough to secure their reality and their complete adequacy; in
order to be adequate they must, further, exactly conform to the meaning
connected with their names by their author, or in common use. Simple
ideas are best off, according to Locke, in regard both to reality and to
adequacy. For the most part, it is true, they are not accurate copies of
the real qualities, of things, but only the regular effects of the powers
of things. But although real qualities are thus only the causes and not
the patterns of sensations, still simple ideas, by their constant
correspondence with rea