Hume, D. (1896) A Treatise of Human Nature, Book I, Part IV, sections ii. Urbana, Illinois: Project Gutenberg. (Original work published in 1739)
Skepticism = the view that we do not have any knowledge. there is no real difference between knowledge and mere belief, and that our beliefs can never be justified in any way that knowledge would require
There are localized versions of skepticism that are less extreme. E.g. a kind of localized skepticism may claim that we don’t have any empirical knowledge of x but we have a priori knowledge about y
Cartesian-Skepticism An alternative approach to the issues outlined by Hume is given by Russell-on-existence-of-external-objects
Hume’s view on the issue of the external world = Hume believes that the senses provide no rational basis for our belief in external objects. But we cannot avoid these beliefs and should acknowledge them as non-rational effects of our faculty of imagination.
“[senses] give us no notion of continued existence, because they cannot operate beyond the extent, in which they really operate. They as little produce the opinion of a distinct existence, because they neither can offer it to the mind as represented, nor as original.”
Hume’s view of philosophy = Hume believes philosophy serves as a kind of skeptic critic that emphasizes the rational shortcomings of our belief system. It doesn’t undermine that belief system because Hume thinks that we’re not capable of casting off our fundamental beliefs anyways. Philosophy serves to show that there are rational shortcomings and that we do believe things irrationally.
Humean skepticism about the external world
Hume is a skeptic because he believes there’s an unbridgeable gap between the evidence that our senses supply and the beliefs we form on the basis of that evidence
He raises two questions on the matter:
- “why we attribute a continued existence to objects, even when they are not present to the senses”
- “why we suppose them to have an existence distinct from the mind and perception”
“These two questions concerning the continued and distinct existence of body are intimately connected together. For if the objects of our senses continue to exist, even when they are not perceived, their existence is of course independent of and distinct from the perception: and vice versa …” (p. 1)
Hume argues that the continued and distinct existence of external objects is not rationally supported by our sensory impressions. There is a gap between what we perceive and what we believe about external objects.
Skeptical argument concerning the continued existence of bodies
He argues that the senses can’t prove that bodies continue to exist beyond being perceived as its a contradiction.
“For that is a contradiction in terms, and supposes that the senses continue to operate, even after they have ceased all manner of operation.” (p. 1)
Sensory impressions are fleeting and intermittent, lasting as long as the sensation lasts. E.g. if you perceive a pencil by touch, that perception of the pencil will only last as long as you touch it. Since sensory information itself has no continued existence beyond the time we’re conscious of it, then it is a contradiction to assume that our senses could give evidence of a bodies continued existence.
Another way of saying it = there is nothing in our sense experience that tells us an object continues to exist when we stop perceiving it
Skeptical argument concerning the distinct existence of bodies
Can the senses establish that external objects exist distinctly from our consciousness of them (are they mind independent?)
Hume highlights two possible views that gives us the notion of distinct existence:
- offer it as represented
- offer it as original
Argument against representationalism
”… To offer it as represented, they must present both an object and an image.. (p. 3)
representationalism = the view that sensory impressions provide us with internal representations of external objects. When you perceive a tree, you are not directly aware of the tress itself. Instead you are aware of the mental representation of the tree and that mental impression represents the real tree. This explains distinct existence as our perceptions representing external objects that exist on their own.1
Hume disagrees with representationalism’s explanation because, for him, representationalism assumes what it tries to prove.
“That the senses offer not their impressions as the images of something distinct, or independent, and external, is evident: because they convey to us nothing but a single perception, and never give us the least intimation of anything beyond. A single perception can never produce the idea of a double existence, but by some inference either of reason or the imagination.” (p. 2)
Ordinarily we can distinguish between a representation and the thing it represents only when both fall within our experience. E.g. we can compare a picture of a tree and the tree itself because we direct access to both. But if all our perceptions are merely internal impressions, then our senses could never represent something beyond them. We never actually perceive external objects themselves, only our impressions of them. Thus, representationalism presupposes the distinct existence of external objects that we have no way of directly perceiving.
Argument against perception = external object
sensory impressions themselves are distinct from our consciousness of them. This is the common sense view that the things we perceive exist just as they appear i.e. the perceptions themselves are the external objects and there is no distinction between the idea and the object.
”… To make it appear as original, they must convey a falsehood; and this falsehood must lie in the relations and situation: In order to which they must be able to compare the object with ourselves…(p. 3)
Hume argues against this view in several ways. First, we recognize that sensory impressions are by nature, internal to our consciousness. So, if they present as external, that must be some kind of “fallacy and illusion” as Hume puts it.
Another point is in order for a sensory impression (X) to appear external to me, you would need the impression of X itself and some impression of myself in order to recognize that something is outside of my consciousness.
“…properly speaking, ‘tis not our body we perceive, when we regard our limbs and members, but certain impressions, which enter by the senses; so that the ascribing a real and corporeal existence to these impressions, or to their objects, is an act of mind as difficult to explain, as that which we examine at present.” (p. 3)
The problem is that the “impression of myself” is just another range of sensory information which is fleeting and intermittent. Appealing to impressions of my body to explain how impressions can appear external is circular = you can’t use more sense impressions to explain how any sense impression can appear external to the mind because the body itself (that is being used as the reference point) is also only given through sensory experience
How are beliefs in external objects justified?
If sensory experience cannot justify the our ordinary beliefs in external objects, how else might such beliefs be justified?
Two possibilities:
- beliefs are justified by reasoning/inference from our sense impressions.
- beliefs are simply not justified and are due to our imagination
Hume points out that people naturally believe in sense perceptions (colors, sound, etc.) that belong to external objects, and that this belief does not come from reason or any deliberate philosophical reflection. The rational arguments constructed by philosophers for the existence of the external world are not known or used by ordinary people (“the vulgar”). Our source of belief for external objects has to be something other than understanding i.e. psychological / habit. He believes that an enduring, mind independent external object is just a projection of our imagination.
He also notes that common sense (the “vulgar: view) and philosophy lead to opposite conclusions.
See Inductive-inferences for Hume’s view on how our knowledge beyond perception can be justified
Footnotes
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this is my own words of representationalism and how it supports the distinct existence of objects ↩