In lieu of an abstract, here is a brief excerpt of the content:Locke on the Knowledge of Material Things ROBERT FENDEL ANDERSON IT IS nOT John Locke's intention, in his Essay Concerning Human Understanding, to deal with matter and material substance nor with how these are able to affect the mind. These are considerations for natural philosophy; Locke counts himself rather among the moral philosophers. He does not propose, therefore, to meddle with the physical aspects of the mind, nor with (...) the physical production of sensations through the organs, nor with the production of ideas in the understanding, nor even with whether ideas depend upon matter for their source. He defers to the wisdom of such men as Boyle, Sydenham, Huygens and Newton in these considerations, and finds it "... ambition enough to be employed as an under-labourer in clearing the ground a little, and removing some of the rubbish that lies in the way to knowledge....,, 1 It is true that Locke's Essay is characterized chiefly not by an interest in matter and the mechanics of perception but rather by an interest in epistemology and in the ordering and assessment of our knowledge. Because of the very nature and emphasis of this epistemology, however, Locke finds that he must, from time to time, at least mention the nature of matter and how it affects us. Finally, it becomes apparent, certain changes or ambiguities in his point of view regarding the mode of our knowledge and its certainty are consequences of his understanding of matter. It is a demonstration of these elements of his doctrine, which seem not to have obtained the full attention of such scholars as Aaron, Fraser, and Gibson, that I shall attempt in this paper. Fundamentally, Locke's theory of matter appears to be that of Democritus and Epicurus. Like the Greek atomists, he conceives of matter as consisting of particles or corpuscles infinite in number. At least some of these are so minute as to be individually insensible, and probably he intends that all are, although, to my knowledge, he never states that this is so. In the aggregate, in any case, particles do constitute perceptible bodies. As for the Greeks, so also for Locke, the particles arc all extended, having size and shape. They are said also to possess motion or rest, although he takes care to say that matter cannot produce motion in itself,e Locke frequently mentions other properties as being "primary" or "really in" material things. Some of these are solidity, texture, cohesion of parts, situation, and number. Apparently some of these may be ranked under others since, as he 1"Epistle to the Reader," Vol. I, p. 14. All footnotes refer to passages in John Locke's An Essay Concerning Human Understanding, collated and annotated, with prolegomena, biographical, critical, and historical by Alexander Campbell Fraser, in two volumes (New York, Dover Publications, Inc., 1959). Large Roman numerals refer to books of the Essay; small Roman numerals refer to chapters of the books; Arabic numerals refer to sections of the chapters. 2 IV, x, 10. [205] 206 HISTORY OF PHILOSOPHY remarks, figure presupposes extension, and receiving or communicating motion through impact presupposes solidity. The influences of these particles upon one another are treated by Locke under the topic of "powers," a notion which includes in it some kind of "secret relation of parts." 3 The capacities in any substance to give alterations of primary qualities are active powers; the capacities to receive such alterations are passive powers. This alteration must be accomplished by impact or impulse since this, Locke says, is the only way in which bodies can be conceived to operate. Sensation in the percipient being then is to be understood as a special case of this impact of particles upon others. It is evident to Locke that from external obiects some motion must be conveyed by some parts of our bodies to the brain or seat of sensation to produce in our minds the particular ideas we have of these external objects. We are able by sight to perceive at a distance the primary qualities of bodies of observable size. Locke reasons that therefore "... some singly imperceptible bodies must come from them to the eyes, and thereby convey to... (shrink)