Locke's Theory of Sensitive Knowledge (review)

254 HISTORY OF PHILOSOPHY Kathleen M. Squadrito. Locke's Theory of Sensitive Knowledge. Washington, D.C.: University Press of America, 1978. Pp. iv + 187. $8.50. Squadrito's book is critical but constructive. Aaron, Collins, Copleston, Jackson, Mandelbaum, O'Connor, Yolton, and others are taken to task for ascribing to Locke views on a variety of topics that Squadrito thinks are misguided or false. She attempts to provide an interpretation of Locke consistent with the Essay and his exchanges with his contemporaries. Beginning with the celebrated definition of knowledge as "the perception of the connection of and agreement, or disagreement and repugnancy of any of our ideas," traditional interpreters conclude that on Locke's view one cannot substantiate any claim concerning sensitive knowledge of the extramental existence of physical things, that one is limited to having ideas and perceiving their relationships to each other. One never perceives physical objects but only ideas which (presumably) are produced by such things. Since one can never break out of the circle of ideas, one can never be assured of the reality of sensitive knowledge or of the existence of physical objects. Arguing that Locke was perfectly aware of the difficulties of such a view--having himself raised the obvious objections against Malebranche--Squadrito shows cause for rejecting such an interpretation of Locke. Positively, it is argued that Locke advances a representative theory of knowledge according to which, in sense perception, one is directly acquainted with physical objects and their properties. Squadrito ascribes to Locke the view that all ideas are signs. For a sign to signify one must be aware both of it and of that of which it is the sign. Since ideas are signs which make objects known, one does not have to deal with the traditional quandary of how to break out of the circle of ideas. This interpretation of Locke is viewed as consistent with his rejection of traditional and Cartesian philosophy. To support her criticism of the traditional interpretation of Locke, Squadrito re-examines his account of ideas both their ontological status and epistemic function. In doing so she argues that for Locke (I) ideas are not modifications of the mind; (2) ideas do not stand as a screen between the mind and physical things; (3) the passive character of the mind in receiving simple ideas is a guarantee that such ideas correspond to the properties of real things in the world; (4) complex ideas of substances are determined by how our minds combine and organize such simple ideas; (5) some complex ideas do not adequately represent things, thus allowing for scepticism concerning what things are; and (6) a re-examination of the distinction between real and nominal essence is a necessary condition to understanding the type of scepticism inherent in the Essay. It is sometimes claimed that if Locke holds a representative theory of perception his distinction between primary and secondary qualities cannot be justified since primary qualities are necessarily imperceptible. Squadrito argues that such a view is not warranted by what Locke says about primary qualities and perception. It is argued that Locke's claim that ideas of primary qualities resemble primary qualities in things really means that such qualifies belong to bodies non-relationally and that our perception of such qualities reveals them as neither ideas in the mind nor as mere powers in objects. Secondary qualities are construed relationally as powers in things to cause ideas in the observer. A traditional criticism of Locke, early raised by Stillingfleet, is that his definition of knowledge as the perception of agreement or disagreement of ideas does not account for sensitive knowledge of physical things. Squadrito argues that the definition given in Book IV is elliptical and can be given the precision needed to accommodate such knowledge. Disregarding the text of the Essay and citing Locke's reply to Stillingfleet, it is argued BOOK REVIEWS 255 that sensitive knowledge involves the perception of the agreement between an "idea of actual sensation" and the "idea of actual existence of something without me that causes that sensation." The passivity of mind in receiving such ideas and the mind's inability to create simple ideas is the guarantee that such...