73. The reason why the sensibility left to itself, renders all its impressions objective, is to be looked for in the fact, that being a non-reflective faculty, it cannot distinguish between a purely internal affection, and one coming from without. Since comparison, however inconsiderable it may be, always implies reflection, sensibility does not compare. Hence it happens that when the subject does nothing but feel, it cannot appreciate the differences of sensations, by calculating the degrees of their vividness, nor ever perceive the existence or want of order and constancy in their connection. The faculty of feeling is perfectly blind to all but its determinate object; whatever it does not discover in this so far as it is its object, does in no manner exist for it. We can now see why, when left to itself, it will render its impressions objective, and believe itself intuitive by converting simple appearances into realities. 74. It is worthy of notice, that of the sensitive faculties, some would always be intuitive, that is, would always refer to an external object, if reflection did not accompany them; whilst others would never be intuitive, not even if separated from reflection, or unaccompanied by those which are by their nature intuitive. To the former class belong the representative faculties, properly so called, that is, those which affect the sensitive subject by presenting to it a form, the real or apparent image of an object. Such are those of sight and of touch, which can neither exist nor be conceived without this representation. Other sensations, on the contrary, offer no form to the sensitive subject; they are simple affections of the subject, although they proceed from an external cause; if we refer them to objects, this we do by reflection; and when this warns us that we have in attributing to the object not only the principle of causality, but also the sensation in itself, carried the reference too far, we easily recognize the illusion, and lay it aside. This does not occur in representative sensations; no one, no matter how great efforts he may make, will ever be able to persuade himself that beyond himself there is nothing real, nothing resembling the sensible representation in which objects are presented as extended.