83. If we reflect upon an azure object, evidently the idea of color enters into that of azure; but without reflection we shall not distinguish the genus, color, and the difference, azure. These two things are not really distinguished in the object perceived; for it would be ridiculous to pretend that in a particular azure-colored object, color is one thing and azure another. Nevertheless we can, when we reflect upon the object, very easily distinguish between the two ideas of color and azure, and we can discuss one without paying attention to the other. Must we say we have the idea of color in general, prior to the sensible representation? Most certainly not: it is only necessary to recognize an innate force of the mind to generalize what is presented to it in particular, and to decompose a simple object into various ideas or aspects.
84. Our understanding is endowed with an intellectual force, by virtue of which it can conceive unity under the idea of multiplicity, and multiplicity under the idea of unity. We discover an example of the latter when we unite what is really multiple in a single conception. Our understanding may be compared to a prism which decomposes a ray of light into many colors; hence different conceptions relating to one simple object. When multiplicity is to be reduced to unity, the intellectual force operates in an altogether contrary manner; instead of dispersing, it unites; the variety of colors disappears, and the ray of light is restored in all its purity and simplicity.
85. Our mind, from the fact that it is limited to know many things by conceptions only, and not by intuitions, requires the faculty of composing and decomposing, of seeing a simple thing under distinct aspects, and of joining different things under a common reason.
We must not fail to observe that the power of generalizing and of dividing, given to our understanding, is a great help to it, indicating, however, its weakness in the intellectual order, and continually warning it to proceed with due circumspection, when it has to decide upon the intimate nature of things.
86. According to this doctrine, general, and more particularly indeterminate ideas result from the exercise of reflection upon our own perceptive acts; and there is in the general idea nothing more than is seen in the particular perception, excepting its own generality produced by the elimination of all individuating conditions. This is especially verified in the idea of being, which, as we have seen, enters as a necessary condition into all our perceptions, and is, moreover, requisite to all operations as well of composition as of decomposition.
We cannot conceive, without conceiving some thing, a being; and this is substantive being. We cannot affirm or deny without saying, is, or is not; and this is copulative being. The idea of being is, therefore, less an idea than a condition necessary to enable our understanding to exercise its functions; it is not a type representing nothing determinate; it is rather the very condition of its life, without which it cannot possibly exercise its activity.
87. But we can, by reflection, perceive this condition of all our thoughts; the idea of being, standing, as it does, involved with the others, is then presented purified to our eyes, and we conceive that general reason of being, or thing, which enters into all our perceptions, but which we had not previously distinguished with sufficient clearness.