Spinoza says:—"By an adequate idea, I understand an idea which, considered in
itself, without relation to the object, possesses all the properties and
intrinsic characters of a true idea" (Ethics,-pt. II. defin. 4). He explains:—"I
say intrinsic, in order to exclude that work which is extrinsic, namely, the
agreement between the idea and its object (ideato)" (Ethics, pt.
II. defin. 4).
According to prop. 35, "Falsehood consists in the absence of the cognition
which inadequate or imperfect and confused ideas involve."