ambiguous, for the effect might be produced either by a painting or by a real key. Without sufficient attention, I inferred that it was a key, when I ought to have examined it more carefully. But my senses did not deceive me, for the eye testified truly, and when I applied to another sense, it enabled me to form a true judgment. I was misled by my own negligence, and not by any defect in my senses. I ought, perhaps, to add that the deception in this case was aided by my companion, who directed my attention to the door, and asked me to hand him the key that he might open it. Had it not been for this circumstance, I should probably have discovered the truth from the effect of binocular vision. It will be found that all the cases which are commonly ascribed to deception of the senses are of the same character as that to which I have here referred. Our senses always testify truly, but we sometimes deceive ourselves by the inference which we draw from their evidence. The defect resides in our inference, and not in our senses, for it is by the use of our senses, alone, that we are enabled to correct the error into which we have fallen by our own inadver tence. REFERENCES. Original and acquired perceptions-Reid's Inquiry, chap. 6, sec. 20— 23. Abercrombie, Part II., sec. 1. Improvement of the senses - - Reid, Essays on the Intellectual Powers Essay 2, sec. 21. SECTION X. OF THE NATURE OF THE KNOWLEDGE WHICH WE ACQUIRE BY THE PERCEPTIVE POWERS. HAVING, in the preceding sections, treated of the manner in which our knowledge of the external world is acquired, I propose, in the present section, to offer some suggestions on the nature of this knowledge. 1. The knowledge which we acquire by perception is always of individuals. If we see several trees, we see them not as a class, but as separate and distinct objects of perception. If we see several men, as John, James, Edward, we see each one as a distinct individual. The same remark applies to the acts which we observe. We see John strike James; that is, we see a particular individual perform a particular act. We thus see, that while, from the knowledge gained by the perceptive faculties, we subsequently form genera and species, yet, without the aid of some other powers of the mind, to form genera and species would be impossible. Our several items of knowledge would be like separate grains of sand, without cohesion and without affinity. 2. The knowledge derived from the perceptive powers is always knowledge of the concrete. When we perceive a body, we do not cognize the color, figure, temperature, etc., each as an abstract quality, and then afterwards unite them in one conception; but we perceive a body, colored, of such a figure and temperature; that is, a body in which all these qualities are united. The first impression made upon us is the cognition of an external object possessing all these qualities; or, at least, so many as are cognizable by the senses which are at the time directed towards them. We have the power of separating these qualities, in thought, the one from the other, and of making each of them a distinct object of attention. This, however, is the function of a faculty of the mind to be treated of hereafter. 3. Of primary and secondary qualities. It has been already stated that our knowledge is of qualities, not of essences. We do not cognize the objects around us absolutely, we cognize them as possessed of certain means of affecting us, and thus giving us notice of the modes of their existence. The qualities of matter have, of old, been divided into two classes, which, at a later period, have been denominated primary and secondary. The primary qualities are those which, by necessity, enter into our notion of matter; which we must conceive of as belonging to body, as soon as we conceive of body at all. Such are extension, divisibility, magnitude, figure, solidity, and mobility. We cannot think of matter, without involving these qualities in our very notion of it. If we conceive of matter as the only thing created, before any sentient being was created to cognize it, we think of it as possessing all these qualities in as perfect a manner as at present. The secondary qualities are those which are not necessary to our conception of matter as matter, yet which give it the power of variously affecting us as sentient beings possessed of such or such an organism. Such are smell, taste, sound, color, hardness, softness, and many others. These might all be absent, or wholly unrecognized, and yet our idea of matter as matter would be definite and precise. They are only cognized by means of their appropriate media. If the media had not been created, no conception of them could ever have been formed. We cognize them only by means of our peculiar organism. Had this organism been created of a different character, these qualities could never have been known. Of the primary qualities themselves we form a definite idea; we know that they are what they seem to us to be. Of the secondary qualities, in themselves, we know nothing more than this, that some occult cause possesses the power of affecting us by means of our senses in this or that manner, or of creating in us such or such cognitions. These secondary qualities have been, more lately, very properly divided into two classes. First, those which we cognize by their relation to our own organism: and, secondly, those which we cognize by their relations to other bodies. Thus, malleability, ductility, and various other qualities, are cognized by the action of various metals on each other. Gold and steel are, to our organism, equally unmalleable; that is, we can make no impression upon either by voluntary effort. But when gold is brought into forcible contact with steel, its quality becomes manifest. The same is true of brittleness, and various other qualities. Sir William Hamilton, after examining this subject with unsurpassed acuteness, has suggested another classification of the qualities of matter. It will be found, treated of in full, in note D to his edition of the works of Dr. Reid. To pursue the subject at length, would be impossible within the limits that must be assigned to the present work. I shall attempt no more than to present a condensed view of some of the most important elements of his classification. Sir William Hamilton divides the qualities of matter into three classes. First, primary or objective; second, secundoprimary or subjecto-objective; and third, secondary or subjective qualities. The primary are objective, not subjective, percepts proper, not sensations proper; the secundo-primary are both objective and subjective, percepts proper and sensations proper; the secondary are subjective, not objective, sensations proper, not percepts proper. 1. Of the primary qualities. These are all deducible from two elementary ideas. We are unable to conceive of a body except, first, as occupying space, and second, as contained in space. From the first of these follow, by necessary explication, extension, divisibility, size, density or rarity, and figure; from the second are explicated incompressibility absolute, mobility, situation. 2. The secundo-primary. These have two phases, both immediately apprehended. "On their primary or objective phasis, they manifest themselves as degrees of resistance opposed to our locomotive energy; on their secondary or subjective phasis, as modes of resistance, a presence affecting our sentient organism." "Considered physically, or in an objective relation, they are to be reduced to classes corresponding to the different sources, in external nature, from which resistance or pressure springs. These sources are three. I. Co-attraction. II. Repulsion. III. Inertia. From cohesion follows, 1. Hard and soft; 2. Firm and fluid; 3. Viscid and friable; 4. Tough and brittle; 5. Rigid and flexible; 6. Fissile and infissile; 7. Ductile and inductile; 8. Retractile and irretractile; 9. Rough and smooth; 10. Slippery and tenacious. From repulsion are evolved, 1. Compressible and incompressible; 2. Resilient and irresilient. From inertia are evolved, Movable and Immovable. 3. The secondary qualities. "These are not, in propriety, qualities of bodies at all. As apprehended, they are only subjective affections, and belong only to bodies in so far as these are supposed furnished with the powers capable of specifically determining the various parts of our nervous apparatus to the particular action, or rather passion, of which they are susceptible; which determined action or passion is the quality of which we are immediately cognizant; the external concause of that internal effect remaining to the perception altogether unknown." "Of the secondary qualities," that is, those phenomenal affections determined in our sentient organism by the agency of external bodies, "there are various kinds; the variety |