This distinction of idea as act and as representative object, pervades the whole body of Cartesian literature. Thus, to take an example, “Every concept or idea,” says Clauberg, “has a twofold dependence: the one from the conceiving and thinking intellect, in as far as it is an act; the other from the thing conceived or like, of which, to wit, it is the representation or image, or whence it is struck out by imitation.”—Op. P. II p. 607 (Ed. 1691). Con. De la Forge, De l’Esprit, chap. X pp. 128, 131. Flenderus, Logica Contracta Claubergiana (4th ed.) § 5, p. 12.
Idea has thus with the Cartesians a twofold relation or dependence (realitas, perfectio, esse, dependentia). In so far as it is an act or mode of the mind (operatio mentis, intellectus), idea possesses a formal and proper being (esse formale seu proprium); in so far as it is the representation of the object thought (imago rei cognitatae), or in the place of that object (in vice illus), it has an objective or vicarious being (esse objectivum sive vicarium). Again, idea, as standing in this double relation or dependence, is said to have a twofold cause, viz., an efficient and an exemplary. In so far as a mode of consciousness, the idea has its efficient cause in intellect or in the mind itself (uti operans suae operationis causa); in so far as representative, the object is the exemplary cause, standing in relation to the idea as the archetype to the ectype, the principal to the vicarious.
It is the discrimination of idea as a mental operation or representative object, which affords the logical distinction of perception and idea, to be met with on all hands in Cartesian literature. “By the term ‘idea,’ ” says Descartes himself, “I understand that form of any thought by the immediate perception of which I am conscious of that same thought.”—Appendix, Def. II p. 229.
“I have said,” says Arnauld, “that I take perception and idea for the same thing. It should be observed, however, that this thing, although one, has two relations: the one to the mind which it modifies, the other to the thing perceived, in so far as it is objectively in the mind, and that the word ‘perception’ more distinctly marks the former relation, and idea the latter. Thus, the perception of a square marks more directly my mind as perceiving a square; and the idea of a square marks more directly the square in so far as it is objectively in my mind.”—Des Vraies et des Fausses Idées, chap. V Def. 6. Con. De la Forge, De l’Esprit, chap. X pp. 128, 140.
It should be observed, however, with regard to this distinction of idea and perception, that with Descartes perception is sometimes used where, in accordance with the propriety of language, we should have expected idea. Thus he says, “The mind always receives these (its perceptions) from the things represented by them.” (De Pass., P. I art. 17.) On the other hand, we find idea where, in accordance with his general nomenclature, we should have looked for perception. “When I will and fear, because at the same time I perceive that I will and fear, the volition itself and fear are reckoned by me among ideas.”—Ob. et Resp. Tertiae, Ob. V p. 98 (Ed. 1670).
Looking to ideas as the immediate objects of knowledge or perception, and considering them in relation to the faculties of which they are the objects, they may be classed as ideas of sense, of imagination, and of the pure intellect, in the exercise of each of which powers we are said to be apprehensive or percipient of ideas. But, as the objects of these powers, ideas differ both in their origin, and according to the character of the objects they represent. In the first relation, ideas arise either simply from the mind, as those of the pure intellect, or from the mind on occasion of body, modified by the corporeal species, as those of sense and imagination. Considered as to their origin, the ideas of sense and imagination thus stand in contrast to those of the pure intellect, for in sense and imagination there is always a physical impression or corporeal species as the cause or occasion of the mental idea; whereas the intellect, as deriving its ideas from the mind itself, has no need of a material organ or of corporeal species. The ideas of sense and imagination, while they agree in being the result, though hyperphysically determined, of a physical antecedent in the form of the corporeal species, and thus in both depending on the bodily organism, nevertheless differ in this, that the species to which the idea is attached is in the case of sense immediately dependent on the presence and action of external objects; while in imagination it depends only remotely on external objects, and proximately on the will, the memory, and the action of the animal spirits.
But the chief contrast of ideas arises from the character of the objects they represent. In this relation, on the Cartesian doctrine, ideas fall into two great classes. The first comprehends all ideas of the individual and picturable, in other words, all the objects of sense and imagination; the second contains
