[CHAPTER XXX.]
PASSIVE SENSIBILITY.
210. Active sensibility, or the faculty of perceiving by the senses, has been a subject of great dispute among philosophers. Passive sensibility, or the capacity of an object to be perceived, is a question of not less interest.
Can every thing which exists be perceived by the senses?
Before answering this question, let us remember that to be perceived by the senses may be understood in two ways: First, it may mean, to cause an impression in a sensitive being; and secondly, to be the immediate object of sensible intuition. The first is true of every being capable of producing the impression; the second is true only of those beings which unite the conditions which the intuition supposes.
211. To produce an impression is simply to cause; and causality is not repugnant to simple beings. There is, therefore, no absurdity in supposing that pure spirits can produce sensible impressions: were it otherwise God could not act upon our soul, causing an impression in it, without the mediation of bodies. This causality cannot be called passive sensibility; the being which has it is not perceived by the senses. The relation of the sensation to the being which produces it would be only that of an effect to its cause.
212. To be the immediate object of sensible intuition, is to be presented to this intuition as an original to the copy. Under this view, only the extended can be perceived by the senses; that is to say, multiplicity combined with continuity is an absolutely necessary condition of our sensitive faculties in relation to external objects.
213. In this manner, it is a manifest contradiction to say that the simple can be sensible. Instinct and reason force us to suppose a real object of sensible intuition. This intuition is referred to the object as to something essentially composite, belonging to the order which we call continuity. If we make this object simple, it ceases to be sensible; and we both affirm and deny its sensible objectiveness. It is a contradiction to suppose a faculty in act, and at the same time to deprive it of the conditions to which its action is necessarily subject.
214. It may be said, that there is no necessity of transferring to the object the conditions of the subject, and therefore a simple object may be presented to the senses. But this is to elude the question at issue. For, either the sensible intuition is referred to the object, or it is not; if it is, the object cannot be simple; if it is not, we fall into idealism, which we have so often combated in the course of this work.
215. If you answer, that our soul, which is simple, has the representation of the composite, I reply, that the objective representation is not the same thing as the subjective perception of the composite; nor the presentation of the object as multiple the same thing as the perception of the multiple. Our soul perceives the multiple, and for this reason must itself be one, or it could not perceive that which is multiple. So much for the subjective; as to the objective, we must remark, that our sensible representations do not always proceed from real objects; but they always refer to objects which are at least possible; that is to say, the intuition is never entirely void; and when it has no object in reality, it finds one in possibility.