Descartes vs Hume

Descartes divides ideas into three kinds: innate ideas, adventitious ideas, and factitious ideas. He says, “among my ideas, some appear to be innate, some appear to be adventitious, and other have been invented by me. My understanding of what a thing is, what truth is, and what thought is, seems to derive simply from my own nature. But my hearing a noise, as I do now, or seeing the sun, or feeling the fire, comes from things which are located outside me, or so I have hitherto judged. Lastly, sirens, hippogriffs, and the like are my own invention.” The categories are determined by what appears to him to be differences with respect to the origins of their contents. The first category poses no difficulties, because Descartes says that he can account for these ideas and their contents by appeal to his own nature; specifically, the idea of what a thought is. The last category of idea also poses no difficulties because he can easily account for them again by an appeal to himself. However, adventitious ideas do pose a problem, since he says that nature has always taught him to think that they are “derived from things that existing outside me.” Therefore, an account of their origin may have to include an appeal to things that exist external to his mind. Hume’s theory of the mind owes a great debt to John Locke’s ideas. Hume names the basic contents of the mind as “perceptions,” as what Locke described as “whatsoever the mind perceives in itself, or is the immediate object of perception, thought or understanding.” Hume divides perceptions into impressions and ideas. The difference between the two are marked by a difference of forcefulness and vivacity, so that impressions relate roughly to “feeling” as ideas relate to “thinking.” “Feeling” here should be understood broadly, and Hume divides impressions into those of “sensation” and those of “reflection.” Impressions of sensation derive from our senses, impressions of reflection derive from our experience of