David Hume (1711-1776): Empiricism, Induction, Skepticism, and Probability 

& Overview

"[M]any advantages . . . result from an accurate scrutiny into the powers and faculties of human nature." (I:.249)

JTB Illustrated: 
-T: "I know G. W. Bush is President", I think. (Suppose he just resigned & Cheney just took the oath of office!). 
-B: I don't know my sweetie is cheating on me -- I don't believe it! (despite J and, alas, T)
-J: I just know that this year the Tigers really are going to win the pennant. (Suppose I think this every year,, and I have no more basis for thinking it this year than these others, but this year, they actually do!) 

  • Preliminaries: Epistemological Focus
    • Knowledge as JTB: Issue of Justification
    • Skepticism: skeptic about X denies there's any JTB about X.
  • Standard Summary: carried Locke's empiricism to it's inevitable skeptical conclusion
    • RE: Substance
      • something I know not what (L)
      • no matter (B), never mind (H)
    • RE: Causation
      • idea of necessary connection entirely empirically baseless, hence
      • the rational basis of induction (probable inference) called into doubt
  • Additional Doctrines of Note
    • (dis)solution of the "free will" problem: free will & determinism are compatible
    • Hume's Fork (c.f., Leibniz, Locke): knowledge is either
      • of matters of fact: synthetic & informative
      • of relations between ideas: analytic and factually uninformative
    • RE: Ethics 
      • H's Law: An "is" cannot entail an "ought"
      • Morality is a matter of "Sentiment or mental Taste"
    • RE: Religion
      • miracles: reports of miracles can never rationally warrant belief
      • Argument from Design is unsound
  • Skeptical Critique of the Self {1}{2}
    • no impression of any enduring subject of experience
    • self is just a bundle of perceptions {3}
  • Basic Assumptions
    • Empiricism: ideas (or concepts) are entirely sense-impression based.
    • Psychologism: theory of knowledge should describe the operations of the mind by which knowledge is (or isn't) produced. 
      • introspection-based: the mind's "a theatre" {4} {5}
      • reflection is not so easy (contra Descartes) {6}
  1. It must be some one impression that gives rise to every real idea. But self or person is not any one impression, but that to which our several impressions and ideas are supposed to have a reference. If any impression gives rise to the idea of self, that impression must continue invariably the same, through the whole course of our lives; since self is supposed to exist after that manner. But there is no impression constant and invariable. Pain and pleasure, grief and joy, passions and sensations succeed each other, and never all exist at the same time. It cannot therefore be from any of these impressions, or from any other, that the idea of self is derived; and consequently there is no such idea. (Treatise I:4:vi)
  2. For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception. When my perceptions are removed for any time, as by sound sleep, so long am I insensible of myself, and may truly be said not to exist. And were all my perceptions removed by death, and could I neither think, nor feel, nor see, nor love, nor hate, after the dissolution of my body, I should be entirely annihilated, nor do I conceive what is further requisite to make me a perfect nonentity. If any one, upon serious and unprejudiced reflection, thinks he has a different notion of himself, I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continued, which he calls himself; though I am certain there is no such principle in me. (Treatise I:4:vi)
  3. [Selves are] nothing but a bundle or collection of different perceptions which succeed each other with an incomparable rapidity, and are in a perpetual flux and motion. Our eyes cannot turn in their sockets without varying our perceptions. (Treatise I:4:vi
  4. The mind is a kind of theatre, where several perceptions successively make their appearance; pass, repass, glide away, and mingle in an infinite variety of postures and situations.  (Treatise I:4:vi)
  5. The comparison of the theatre must not mislead us. They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place there these scenes are represented, or of the materials of which it is composed. (Treatise I:4:vi)
  6. It is remarkable concerning the operations of the mind, that, though most intimately present to us, yet, whenever they become the object of reflexion, they seem involved in obscurity; nor can the eye readily find those lines and boundaries, which discriminate and distinguish them. (Enquiry I)
  7. [Morality] is entirely relative to the Sentiment or mental Taste of each particular Being; in the same Manner as the Distinctions of sweet and bitter, hot and cold, arise from the particular feeling of each Sense or Organ. (Enquiry I)

II. Origin of Ideas

Vivacity Worry : impressions may be very faint (with things seen in bad light, far away) and hallucinations can be very vivid:. REPLY: "except the mind be disordered by disease or madness they can never arrive at such a pitch of vivacity as to render these perceptions altogether indistinguishable. (Enquiry II)

  • Ideas & Impressions
    • Impresssions are "our more lively pereceptions, when we hear, or see, or feel, or love, or hate, or desire, or will" (Enquiry II)
    • Ideas are "less lively perceptions, or which we are conscious, when we reflect on" impressions.
  • Empiricism: all ideas arise from impressions {1}
    • directly, by reflection (cf. Locke's "simple ideas")
    • indirectly by concatenation: e.g.
      • a golden mountain {2}
      • God {3} 
    • possible exception: shades of color intermediate between two we have experienced might be imaginable without our ever having experienced exactly that color before. {4}
  • Empiricist Criterion of Meaning {5}
    • words without attached ideas are meaningless
    • no idea without constituent impressions
  1. [A]ll our ideas or more feeble perceptions are copies of our impressions or more lively ones. (Enquiry II)
  2. [A]ll this creative power of the mind amounts to no more than the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses and experience. When we think of a golden mountain, we only join two consistent ideas, gold, and mountain, with which we were formerly acquainted. (Enquiry II
  3. The idea of God, as meaning an infinitely intelligent, wise, and good Being, arises from reflecting on the operations of our own mind, and augmenting, without limit, those qualities of goodness and wisdom. (Enquiry II)
  4. [T]his instance is so singular that it is scarcely worth our observing, and does not merit that for it alone we should alter our general maxim" (Enquiry II)
  5. When we entertain ... suspicion that a philosophical term is employed without any meaning or idea ... we need but enquire, from what impression is that supposed idea derived? And if it be impossible to assign any, this will ... confirm our suspicion. (Enquiry II

III: Of the Association of Ideas

  • Principle of Association {1}
  • Evidence of Association
    • trains of discourse or logical thought
    • coherence in even "our wildest . . . reveries": even these run "not altogether at adventures"
    • language argument {2}
  • Three Principles of Connection {3}
    • Resemblence: "a picture naturally leads our thought to the original" (Enquiry III)
    • Contiguity: "mention of one apartment naturally introduces and enquiry or discourse concerning the others" (Enquiry III)
    • Cause or Effect: "if we think of a wound, we can scarcely forbear reflecting on the pain" (Enquiry III
  1. It is evident that there is a principle of connexion between the different thoughts or ideas of the mind, and that in their appear-ance to the memory or imagination, they introduce each other with a certain degree of method and regularity. (Enquiry III)
  2. Among different languages, even where we cannot suspect the least connexion or communication, it is found, that the words, expressive of ideas, the most compounded, do yet nearly correspond to each other: a certain proof that the simple ideas, comprehended in the compound ones, were bound together by some universal principle, which had an equal influence on all mankind. (Enquiry III)
  3. To me, there appear to be only three principles of connexion among ideas, namely, Resemblance,Contiguity in time or place, and Cause or Effect. (Enquiry III)

Doubts Concerning the Operations of the Understanding

11.  In vain do you pretend to have learned the nature of bodies from your past experience. Their secret nature, and consequently all their effects and influence, may change, without any change in their sensible qualities. This happens sometimes, and with regard to some objects: Why may it not happen always, and with regard to all objects? (Enquiry IV)

12.  [I]t is not reasoning which engages us to suppose the past resembling the future, and to expect similar effects from causes which are, to appearance, similar. (Enquiry IV)

13.  Adam, though his rational faculties be supposed, at the very first, entirely perfect, could not have inferred from the fluidity and transparency of water that it would suffocate him, or from the light and warmth of fire that it would consume him. (Enquiry IV)

  • Hume's Fork: Knowledge concerns either {1}
    • Relations of Ideas
      • known a priori: "discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe" (Enquiry IV)
      • their truth is necessary: their opposites would be logical impossibilities or contradictions.
    • Matters of Fact {2}
      • experience required: known a posteriori
      • their truth is not necessary: their opposites are not contradictory, they're logically possible.
  • The Epistemological Problem of Induction {3}: What warrants
    • predictions: the sun will rise tomorrow
    • generalizations: bread nourishes; water freezes at 32F.
  • Concerning our Knowledge of Cause and Effect {4}
    • not a priori {6}{13}
    • based on constant conjunctions of experiences {5}{8}
  • Induction Redux: Regularity of Nature Principle {7}
  • Hume's Skeptical Argument: {9}
    • Would be induction
      • Water has always frozen at 32F in the past.
      • :. Water will continue to freeze at 32F in the future.
    • Unstated Assumption: The Future will be like the past.
    • Unjustifiable assumption {10}
      • not a truth of reason
      • not a truth of fact: its would-be induction would be circular {7}
        • The future always has been like the past, in the past.
        • :. The future will continue to be like the past.
    • Conclusion: our belief in induction has no rational basis -- but only a psychological basis in "custom or "habit" {11}{12}
  1. All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas, and Matters of Fact. (Enquiry IV)
  2. The contrary of every matter of fact is still possible; because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so conformable to reality. That the sun will not rise to-morrow is no less intelligible a proposition, and implies no more contradiction than the affirmation, that it will rise. (Enquiry IV)
  3. [W]hat is the nature of that evidence which assures us of any real existence and matter of fact, beyond the present testimony of our senses, or the records of our memory[?] (Enquiry IV)
  4. All reasonings concerning matter of fact seem to be founded on the relation of Cause and Effect. By means of that relation alone we can go beyond the evidence of our memory and senses. (Enquiry IV)
  5. I shall venture to affirm, as a general proposition, which admits of no exception, that the knowledge of this [cause-effect] relation . . . arises entirely from experience, when we find that any particular objects are constantly conjoined with each other. (Enquiry IV)
  6. When we reason a priori, and consider merely any object or cause, as it appears to the mind, independent of all observation, it never could suggest to us the notion of any distinct object, such as its effect; much less, show us the inseparable and inviolable connexion between them. (Enquiry IV)
  7. We have said that all arguments concerning existence are founded on the relation of cause and effect; that our knowledge of that relation is derived entirely from experience; and that all our experimental conclusions proceed upon the supposition that the future will be conformable to the past. To endeavour, therefore, the proof of this last supposition by probable arguments, or arguments regarding existence, must be evidently going in a circle, and taking that for granted, which is the very point in question. (Enquiry IV)
  8. When a child has felt the sensation of pain from touching the flame of a candle, he will be careful not to put his hand near any candle; but will expect a similar effect from a cause which is similar in its sensible qualities and appearance. (Enquiry IV)
  9. It is impossible, therefore, that any arguments from experience can prove this resemblance of the past to the future; since all these arguments are founded on the supposition of that resemblance. (Enquiry IV)
  10. Let the course of things be allowed hitherto ever so regular; that alone, without some new argument or inference, proves not that, for the future, it will continue so. (Enquiry IV)

V. Skeptical Solution to These Doubts

"All inferences from experience, therefore, are effects of custom, not of reasoning." (Enquiry V)

"All these operations are a species of natural instincts, which no reasoning . . . is able either to produce or prevent." (Enquiry V)

  • Reasonings from experience (or inductions) are not based on reason but instinct or habit or custom {1}
    • the discovery that induction has no rational basis does not cause us to desist from inductive "reasoning"
    • its basis is instinstinctive, not rational
  • Thought experiment re: acquisition of the  idea of causation?
    • "Suppose a person . . . brought on a sudden into this world." 
    • they would observe succession of objects or events but not the causing or necessitating of one by another {2}
  • Conclusion: repeated experiences of constant conjunction form the habit or custom of passing from the thought of the first to the second: "after the constant conjunction of two objects--heat and flame, for instance, weight and solidity-- we are determined by custom alone to expect the one from the appearance of the other. (Enquiry V) {3}
  1. [I]n all reasonings from experience, there is a step taken by the mind which is not supported by any argument or process of the understanding. (Enquiry V)
  2. [A person suddenly brought into the world] would not, at first, by any reasoning, be able to reach the idea of cause and effect; since the particular powers, by which all natural operations are performed, never appear to the senses; nor is it reasonable to conclude, merely because one event, in one instance, precedes another, that therefore the one is the cause, the other the effect. Their conjunction may be arbitrary & casual. (Enquiry V)
  3. [Having] observed familiar objects or events to be constantly conjoined together . . . . He immediately infers the existence of one object from the appearance of the other. Yet he has not, by all his experience, acquired any idea or knowledge of the secre power by which the one object produces the other; nor is it by any process of reasoning, he is engaged to draw this inference. (Enquiry V

VI. Of Probablity

Water always turns to ice at temperatures below 32F.
It's below 32F in my freezer.
So, this water I'm putting in my freezer will surely turn to ice.

Temperatures usually go below freezing on mid February nights in Alma 
It's mid February.
So, probably, the temperature  will go below freezing tonight in Alma

  • Classification of Arguments
  • demonstrations: not based on experience
  • arguments from experience
    • proofs: such arguments from experience as leave no room for doubt or opposition
    • probabilities: such arguments from experience as leave room for doubt or opposition
  • Denial of Reality of Chance {1}.
  • real or metaphysical probability of anything = 1 or 0
  • probability for all we know may be anything in between
  • Two sorts of apparent causes {4}
  • universal or certain: 
    • Fire burns and water suffocates us, always
    • Law of universal gravitation holds without exception. 
  • probable or uncertain: 
    • "nor has rhubarb always proved a purge,
    • or opium a soporific to everyone" (Enquiry VI)
  • Probable v. Deterministic Reasoning
  • Determinism as a scientific-philosophic assumption is irrelevant to our experience-based inferences. {2}
  • Deterministic reasoning is just a special case of probable reasoning where p=1. {3}
    • psychologically similar inferences
    • practically: probabilities must serve 
    • discussion: logical divergence
  1. Though there be no such thing as Chance in the world; our ignorance of the real cause of any event has the same influence on the understanding, and begets a like species of belief or opinion. (Enquiry VI)
  2. It is true, when any cause fails of producing its usual effect, philosophers ascribe not this to any irregularity in nature; but suppose, that some secret causes, in the particular structure of parts, have prevented the operation. Our reasonings, however, and conclusions concerning the event are the same as if this principle had no place. (Enquiry VI)
  3. Being determined by custom to transfer the past to the future, in all our inferences; where the past has been entirely regular and uniform, we expect the event with the greatest assurance, and leave no room for any contrary supposition. But where different effects have been found to follow from causes, which are to appearance exactly similar, all these various effects must occur to the mind in transferring the past to the future, and enter into our consideration, when we determine the probability of the event. (Enquiry VI)
  4. There are some causes, which are entirely uniform and constant in producing a particular effect; and no instance has ever yet been found of any failure or irregularity in their operation. Fire has always burned, and water suffocated every human creature: the production of motion by impulse and gravity is an universal law, which has hitherto admitted of no exception. But there are other causes, which have been found more irregular and uncertain; nor as rhubarb always proved a purge, or opium a soporific to every one, who has taken these medicines. (Enquiry VI)

Next: Hume: Necessity, Causation, Freedom, and Religion