The Facts in the Case.—The truth is, things exist thus and thus, and we are constituted with reference to them as thus existing. Sense and experience inform us of these existences and realities. Some of them are objects of direct perception by the senses, as matter and its qualities. Some of them are not directly objects of perception, but are suggested to the mind by the operations of sense, and are intuitively perceived by the mind, and recognized as truths and realities when thus suggested, as time, space, substance, cause, the right, the wrong, the beautiful, etc.
The mind has the faculty of receiving and recognizing such truths and realities as thus suggested; and this faculty we call the power of original and intuitive conception.
These Ideas of internal Origin, in what Sense.—It has been customary of late, especially in our country, to speak of the class of ideas now referred to as of internal origin, in distinction from other ideas, derived more directly from sense, and which are consequently designated as of external origin. As it is desirable to be exact in our use of terms, it may be well to inquire in what sense any of our ideas are of external, and in what sense of internal origin, and wherein the ideas, now under consideration, differ from any others in respect to their source.
Ideas of external Origin.—A large class of our ideas evidently relate to objects of sense, objects external and material, of which we take cognizance through the senses. Such ideas may be said to be of external origin, inasmuch as they relate to things without, and are dependent on the external object as the indispensable condition of their development. Were it not for the external object producing the sensation of color or of hardness, I should not have the idea of redness or of hardness; were it not for the external object resisting my movements, I should not get the idea of externality. The idea is, in these cases, dependent on, and limited by, the sensation or the perception. They correspond as shadow and substance. The idea of resistance, and the perception of it, the idea of sound or color, and the sensation of it, are coëxtensive, synchronous, and, as to contents, identical.
These, in a Sense, internal.—In another sense, however, even these ideas are of internal origin, that is, they are the mind's own ideas; they spring up in the mind, and not out of it; they are, as ideas, strictly internal states, affections, acts of the mind itself. Take away intelligence, reason, the light divine, from the soul of man, and the external objects may exist as before, and produce the same effect on the organs of sense, but the ideas no longer follow. The physical organs of the idiot are affected in the same way by external objects as those of any other person, but he gets not the same ideas. These, it is the office of the mind to produce and fashion for itself out of the occasion and material furnished by sense. And this is as true of ideas relating to external objects as to any other.
Sensation an internal Affection.—It may even be said of this class of ideas, that their suggestion is of internal origin. The immediate occasion of the mind's having the idea of extension, weight, hardness, color, etc., is not the existence of the object itself, possessing such and such qualities, but the impression produced by the object and its qualities on the sense; in other words, the sensation awakened in us. This it is which awakens and calls forth in the mind the idea of the external object. Were there, for any reason, no sensation, then the objects might exist as now, but we should have no idea of them. But sensation is an internal affection, revealed by consciousness, and the ideas awakened by it and dependent on it, are immediately of internal origin, though mediately dependent on some preceding external condition and occasion.
Ideas of internal Origin.—If we examine, now, the ideas of internal origin, so called, furnished by the faculty of original and intuitive conception, we find that, while they do not directly relate to objects of sense external and material, they nevertheless depend, in like manner, on some preceding operation of sense as the occasion of their development. Observation of what goes on without, or consciousness of what goes on within furnishes the occasion, as all admit, on which these ideas are awakened in the mind. The idea of time, e. g., is connected with the succession of events, external or internal—things without and thought and feeling within following each other—which succession is matter of observation or of consciousness. The idea of space is connected with the observation or sensation of body as extended. The idea of beauty and deformity is awakened by the perception of external objects as possessing certain qualities which we thus designate. The idea of right and wrong in like manner connects with something observed in human conduct. So of all ideas of this class. They are not disconnected with, nor independent of, the appropriate objects of observation and consciousness. These objects must exist, these occasions must be furnished, as the indispensable condition of the existence of the idea in the mind. Dispense with the succession of events or the observation of it, and you dispense with the idea of time in the human mind.
Conclusion.—So far as regards the origin of the ideas in question, it is not easy to draw a dividing line, then, between the two classes, marking the one as external, the other as internal. Both are of external origin, and equally so, in this sense—that they both depend, and equally depend, on some previous exercise of sense as the occasion and condition of their development. Both are of internal origin, in another sense—that they are both awakened in the mind—are both the product of its own activity.
Difference lies in what.—The difference is not so much that of externality or internality of origin, as it is a difference of character. The one relates to objects of sense, which can be seen, heard, felt; the other to matters not less real, not less obvious, but of which sense does not take direct cognizance. In either case they spring from the constitution and laws of the mind. Such is my constitution that external and material objects, affecting my senses, furnish me ideas relating to such objects. And such is my constitution that certain relations and qualities of things not directly cognizable by sense, and certain realities and facts of an æsthetic and moral nature, likewise impress my mind, and thus awaken in me the idea of such relations and realities. The objects, the relations, the realities, exist, they are perceived by the mind, and thus the first idea of them is obtained. Color exists, and the eye is so constituted as to be able to perceive it, and thus the idea of color is awakened in the mind. So right and wrong exist, and the mind is so constituted as to be able to perceive and recognize their existence, and thus the idea of right is awakened in the mind. The faculty we call perception in the one case, original conception in the other.