Although every one who reflects upon his own feelings, must be aware of the difference between an original perception and its idea,* yet it is not easy to the great authority of Prof. Stewart, who defines conception to be "that power of mind, which enables it to form a notion of an absent object of perception:" Elem. ch. iii. v. i. p. 133; but this difference almost unavoidably follows from the mode in which I have thought it necessary to use the term perception. Hume considers "ideas" to be synonymous with "thoughts;" Essays, v. ii. p. 31. Helvetius, whose language on this subject is generally correct, still further restricts the term idea to what I have styled intellectual, corresponding to Locke's ideas of reflection; Sur l'Esprit, t. i. p. 68. I think that a degree of ambiguity has been produced in the writings of some of the modern metaphysicians, by the manner in which they have employed the words simple and compound ideas; the former being appropriated to those that originate in perception, the latter in intellectual operations; Hartley, Introd. p. ii. But, I conceive, that the circumstance of their being perceptive or intellectual has no necessary relation to their condition as being simple or compound. Many perceptive ideas are compounded, i. e. we receive perceptions which are themselves composed of more simple perceptions, and which are impressed upon the mind without any decomposition or analysis. I do not mean by this remark to enter upon the discussion, how far our ideas are, strictly speaking, capable of being compounded, generalized, or abstracted; I only maintain, that the same kind of combination takes place in the one case as in the other. Locke did not make the distinction to which I have referred above; he has complex ideas of sensation, and simple ideas of reflection; Essay, b. 2. ch. 2.. 12. * That state of the mind, in which ideas are mistaken for perceptions, may be regarded as the most unequivocal indication of insanity, as distinct from fatuity, on the one hand, or mere obstinate caprice, on the other. As far as we are to be guided in our conclusions by pathological and anatomical considerations, I should maintain, that in insanity the disease of the mind is frequently independent of, or antecedent to, that of the brain. In delirium we may conceive that the primary disease is in the brain, while in fatuity the brain would appear to be imperfect and incapable of performing its functions. There is also another state, in which the brain is morbidly affected, so as to convey false perceptions to the mind, but where the mind itself is sound, and where the individual is consequently aware of the fallacy of his perceptions. A case of this kind is detailed with great minuteness by Nicolai of Berlin, who was himself the subject of it; Nicholson's Journ. determine precisely in what this difference consists. Hume, who makes this the express subject of enquiry, only observes, that the idea is less vivid and distinct than the primary perception,* an observation which does not afford any adequate solution of the difficulty. But the connexion between perception and ideas, however produced, is one of which we cannot doubt, and it is no less certain, that in some way or other, they are connected through the intervention of the nervous system. v. vi. p. 161. et seq. see also v. xv. p. 288. et seq. Many accounts of spectres, and other supposed miraculous sights and sounds, are to be referred to corresponding changes actually produced upon the brain, although considerably modified by the imagination and credulity of the narrators. This point is very ingeniously elucidated by Dr. Alderson, in his " Essay on Apparitions;" Ferriar, who has subsequently written on the same subject, has not sufficiently distinguished between three sets of causes, all of which may contribute to the result; the peculiar condition of the brain, the mental indisposition under which the individual laboured, and certain natural phenomena, which, without any disease, either of the brain or of the understanding, were not understood, and were therefore referred to some supernatural agency. Cases of this description, where there are false perceptions accompanied by a conviction of their failure, must, I apprehend, furnish an insurmountable objection to Reid's fundamental position, with regard to the mode by which we acquire our knowledge of the external world. On this subject see Parry's Pathology; § 775.. 782, where we meet with many valuable observations, but I think that the author has incorrectly classed this affection as a variety of insanity, to which it is no more entitled, than a false perception proceeding from a morbid state of the nerve of the finger, or any other part of the body. We have a still later work on the "Philosophy of Apparitions," by Dr. Hibbert; it contains much curious information and many valuable remarks upon the different morbid conditions, both of the body and of the mind, which may be supposed to give rise to these appearances; but I think that in some of his metaphysical speculations he is too refined, and that his views may be characterized rather as ingenious, than as correctly deduced from the acknowledged laws of the animal economy. A doctrine not very different from the above is broached by Hobbes in his treatise on human nature, p. 102; a treatise which contains much acuteness of remark, delivered in a quaint and antiquated style. * Essays, v. ii. p. 30, 1. APPENDIX. The conclusion which Dr. Hibbert draws from his enquiry is, "that apparitions are nothing more than morbid symptoms, which are indicative of intense excitement of the renovated feelings of the mind." p. 375. I am disposed to dissent from this definition on two grounds; first, I think that these phenomena are not always the result of intense excitement, and secondly, that they are not simply renovated feelings, i. e. a repetition of previous perceptions. With respect to the first point, I should prefer considering them as morbid symptoms, depending upon some irregularity of the natural functions, and which, according to circumstances, may consist either in an excess, or a defect of the ordinary actions of the system. And with respect to the second, there are, I conceive, in most cases of this description, new perceptions produced, which had never previously existed. Consequently the part of the nervous system, whether the brain or the nerve, which is affected, is brought into a state which it had never before experienced. I am induced to form this conclusion partly from the circumstance from having been myself the subject of this disease. Without going into a minute detail of the case, I shall merely state, that I was labouring under a fever, attended with symptoms of general debility, especially of the nervous system, and with a severe pain of the head, which was confined to a small spot situated above the right temple. After having passed a sleepless night, and being reduced to a state of considerable exhaustion, I first perceived figures presenting themselves before me, which I immediately recognised as similar to those described by Nicolai, and upon which, as I was free from delirium, and as they were visible for about three days and nights with little intermission, I was able to make my observations. There were two circumstances which appeared to me very remarkable; first, that the spectral appearances always followed the motion of the eyes, and secondly, that the objects which were the best defined, and remained the longest visible, were such as I had no recollection of ever having previously seen. For about twenty-four hours I had constantly before me a human figure, the features and dress of which were as distinctly visible as that of any real existence, and of which, after an interval of many years, I still retain the most lively impression, yet neither at the time nor since, have I been able to discover any person, whom I had previously seen, that resembled it. After During one part of this disease, after the disappearance of this stationary phantom, I had a very singular and amusing imagery presented to me. It appeared as if a number of objects, principally human faces or figures, on a small scale, were placed before me, and gradually removed, like a succession of medallions. They were all of the same size, and appeared to be all situated at the same distance from the face. one had been seen for a few minutes, it become fainter, and then another, which was more vivid, seemed to be laid upon it, or substituted in its place, which, in its turn, was superseded by a new appearance. During all this succession of scenery, I do not recollect that, in a single instance, I saw any object with which I had been previously acquainted, nor, as far I am aware, were the representations of any of those objects, with which my mind was the most occupied at other times, presented to me; they appeared to be invariably new creations, or at least new combinations, of which I could not trace the original materials. The circumstance which I at the time considered to be so extraordinary, that the motion of the spectres followed that of the eye, has been also observed by Remarks on the Cause of the Spectral Appearances. 163 Dr. Brewster, and must therefore be regarded, as not so anomalous a fact as I, at the time, considered it to be.* Dr. Hibbert supposes this motion of the spectres to prove that the retina itself is the seat of these morbid impressions, and this is the conclusion which naturally presents itself to the mind on the first view of the subject. But perhaps, upon further reflection, we may find reason to doubt of the correctness of this opinion. In the first place we have no independent evidence of the eye itself being affected in these cases, while there is every reason to suppose that the brain is the primary seat of the disease. And, in the next place, if we enquire why the mental spectres appear to occupy any definite portion of space, why they seem to be on the right side or on the left side, why they appear at the distance of five, ten, or twenty feet, I apprehend that the answer must be, that our judgment is directed by associations previously formed with states of the brain, which, to a certain extent, resemble the present morbid condition. I have, in a former chapter, stated the circumstances which enable us to judge of the visible position and magnitude of objects, and we may suppose that our ideas of visible motion are derived from associations of an analogous kind. I think it would tend to illustrate this subject, if the patient were directed to observe whether the spectres appear to follow the eyes, when the balls are fixed, while the whole of the head is turned round, and likewise what occurs when a degree of vertigo is induced. These observations it did not occur to me to make at the time, nor do I find that they have been made by others. * Journ. of Science, v. ii. p. 8, 9. |