Rene Descartes and John Locke both have similar theories about primary qualities. They both hold the same position on what is that primary qualities are. Both of them believe that primary qualities have the power to cause ideas in our minds. The main distinction between their theories lies in whether primary qualities are perceived by means of the senses or by the intellect.
Rene Descartes believed that there are two types of qualities, primary and secondary qualities. To Rene Descartes, primary qualities are those that are clearly and distinctly perceived by us (33). These qualities are those that exist due to their geometric integrity and which are related to some extension of a body in space. By this reasoning, Descartes believes these primary qualities are composed of anything that is measurable and can have math applied to them such as motion, shape and size. Descartes believes that primary qualities are not misleading like secondary qualities are. This is because the essence of secondary qualities is not geometric and thus these qualities are perceived obscurely. Nevertheless both of these qualities produce ideas within us. The difference about the ideas produced by these qualities lie in whether it is clear and distinct or obscure and confused. The reason that these secondary qualities are often misleading and primary qualities are not is because we perceive both of these qualities differently.
Descartes states that primary qualities, unlike secondary qualities, are perceived clearly and distinctly. This he beliefs, is due to the fact that our method that we go by perceiving these qualities is different. Primary qualities are perceived through our intellect as opposed to secondary qualities which are perceived through our senses (14). Descartes believes that our understanding comes through our intellect and not our senses, therefore the ideas that we are able to grasp from primary qualities are not by means of our senses but rather by means of our intellect since they are clear and distinct unlike those ideas that come from our senses which are obscure and confused. Both primary and secondary qualities are perceived by the mind immediately and therefore result in the ideas we have (32). Unlike secondary qualities, primary qualities are features of the physical objects that are actually there but we come to understand the ideas produced by primary qualities solely by means of our intellect.
Descartes uses the example of a thousand-sided figure to show how primary qualities produce these clear and distinct ideas compared to the often misleading ideas of secondary qualities (sixth meditation). He states that the imagination by means of the senses is able to generate an obscured and confused idea about a thousand sided figure in comparison to the intellect which is able to perceive it clearly no matter how many sides the figure has. These ideas, which are a product of primary qualities are related to extension and are therefore perceived by our intellect using our understanding (sixth meditation). Descartes theory on primary qualities has some similarity to John Locke’s but differs on how it is that these ideas come to be about within us.
John Locke’s point of view regarding primary and secondary qualities is similar to some extent to Descartes’ theory of primary and secondary qualities. To Locke, primary qualities are spatiotemporal and quantitative. Therefore like Descartes, primary qualities are composed of size and shape, something which is measurable (135). Like Descartes, Locke believes that these qualities have the effect of producing the ideas that we have within us. An idea to Locke is the thought or understanding which is produced by the object. He calls the power that an object has to produce such ideas within us, qualities. Locke states that ideas are existent in our minds. To Locke these qualities are properties belonging to the objects and are the cause of the ideas that we house in our minds (134). The difference between primary qualities and secondary qualities to Locke is the kinds of ideas that these are able to produce in our minds. Locke believes that the ideas produced by primary qualities are a resemblance of these qualities. Locke believes that these qualities are actually existent in the objects themselves. On the other hand, those of secondary qualities hold no resemblance to them (136). Unlike Descartes, John Locke has a different theory by which we acquire these ideas.
Unlike Descartes, John Locke believes that we acquire our ideas through the perception of the senses. According to Locke, reasoning is an exception to his perspective on innate ideas. He believes that all of our ideas are acquired through our experiences and by means of our senses. Locke states how our mind is similar to that of a blank state, and it is only by experiences that we are able to perceive by means of our senses that we acquire the ideas we possess. Qualities are the powers that objects have and it is within these powers that ideas are produced by them within us. Primary qualities are inseparable from the object, and thus the power of primary qualities produces ideas that resemble the object. This is shown by the example he gives of when something is divided even into its smallest of parts, even when these are too small for us to perceive, the primary qualities are still existent in the object (138).
Although Descartes and Locke description of what primary qualities are is similar, their belief in how it is that we come to reason or reflect on these qualities is different. Descartes believes that we can’t rely entirely on our senses, since they often deceive us. He believes that those ideas obtained from primary qualities are distinct and clear. Therefore he believes that the ideas produced by primary qualities are grasped by means of the intellect. Locke unlike Descartes believes that the ideas we acquire through our life is by experience and it is by the senses that we come to have such experiences. Therefore to Locke, the ideas produced by the power of primary qualities are grasped by means of the senses. To Locke and Descartes, primary qualities are the causal effect which produces the clear ideas that we have, the main difference between their theories is whether we obtain these through our senses and by reflecting or solely by the intellect.
