Handout 27: Hume’s Skepticism II: The External World
Philosophy 322: Modern Philosophy
Professor Geoff Pynn
Northern Illinois University
Spring 2011
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the “universal and primary opinion of men”

The “natural” or “common” view about the external world and our knowledge of it consists of two parts. First, that the external world exists independently from us; second, that we are directly aware of this world in sensory experience.
Both quotes from the Enquiry, Section XII, Part 1 (AW 594b):
“It seems evident that men are carried by a natural instinct or prepossession to repose faith in their senses, and that without any reasoning, or even almost before the use of reason, we always suppose an external universe which does not depend on our perception, but would exist though we and every sensible creature were absent or annihilated.” 1. It is “natural” to believe that there is a world outside of ourselves; i.e., that:
(a) The world doesn’t depend on my perceiving it in order to exist.
(b) The world would exist even if I didn’t.
(c) The world would exist even if all “sensible creatures” ceased existing.
(Interesting question for Hume: if these beliefs are the result of “natural instinct”, are they innate? In his earlier book A Treatise of Human Nature, Hume gave a very detailed empiricist account of where they came from (in Section i.4.2); short version: they come from the imagination. Now, they simply result from “natural instinct or prepossession”.)
“It seems also evident that when men follow this blind and powerful instinct of nature they always suppose the very images presented by the senses to be the external objects and never entertain any suspicion that the one are nothing but representations of the other. This very table which we see white and which we feel hard is believed to exist independent of our perception and to be something external to our mind which perceives it.”
2. It is also “natural” to take our sensory impressions to be the external objects themselves.
(In the second sentence, Hume is using the phrase “this very table” to refer to our sensory impression of the table—which we naturally take to be the table itself.)
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2 “destroyed by the slightest philosophy”
“But this universal and primary opinion of all men is soon destroyed by the slightest philosophy which teaches us that nothing can ever be present to the mind but an image or perception, and that the senses are only the inlets through which these images are conveyed, without being able to produce any immediate intercourse between the mind and the object. The table which we see seems to diminish as we remove further from it. But the real table which exists independent of us suffers no alteration. It was, therefore, nothing but its image which was present to the mind. These are the obvious dictate of reason and no man who reflects ever doubted that the existences which we consider when we say this house and that tree are nothing but perceptions in the mind and fleeting copies or representations of other existences which remain uniform and independent.” (AW 594b)
1. The big claim here is that philosophical reflections leads to representationalism; the view that: (a) The objects of sensory awareness are “in the mind”.
(b) Those objects represent external (“real”, “independent”) things.
2. Why should we believe that the objects of sensory awareness are in the mind, and not external things?
(a) Hume gives the Argument from Perceptual Variability
i. The “table” present to my mind gets smaller when I move away from it. ii. The real table doesn’t get smaller when I move away from it. iii. So, the “table” present to my mind ̸= the real table. (By Leibniz’s Law)
(b) More famous: the Argument from Illusion
i. Consider the Rotating Snake illusion of Akiyoshi Kataoka. ii. The object I am aware of is moving. iii. The external thing (in this case, the colored shapes on the page / screen) is not moving. iv. So, the