John Locke (1632-1704): Empiricism: Knowledge, Ideas, & Experience



  • Common Sense contra Rationalism
    • In general, absolute certainty is neither necessary nor attainable outside of mathematics {1}
      • witness the insoluble disagreements of the rationalists, about substance, e.g. {2}
        • Descartes: 2 types (+ God): extended & thinking: 1 individual body: infinitely many minds
        • Spinoza: 2 "types" as understood: 1 individual (God or Nature) token 
        • Leibniz: 1 type,  minds: infinitely many individual or tokens
      • observation & trial & error not (just) mathematics required for real-world knowledge: medicine v. mathematics {3}
    • probability is all that's achievable in most connections and is generally sufficient for the conduct of our practical affairs
  • Starting point of inquiry should be inquiry into our own mental powers with an eye to determining their powers and, especially, their limitations. {4}
    • must track ideas back to their source in experience {5}
    • if they have no basis in experience they don't signify anything -- they're just empty words with no thoughts corresponding

1.    If we disbelieve everything because we cannot certainly know all things we shall do . . . as wisely as he who would not use his legs, but sit still and perish, because he had no wings to fly (I: i:5 )

2.    I suspected [on the rationalist plan] we began at the wrong end . . .. Thus . . . extending their enquiries beyond their capacities, and letting their thoughts wander into those depths where they can find no sure footing, it is no wonder that they raise questions and multiply disputes . . . never coming to any clear resolution . . . (I:i:7)

3.    He that in physic shall lay down fundamental maxims, and, from thence drawing consequences and raising disputes, shall reduce it into the regular form of a science, has indeed done something to enlarge the art of talking and perhaps laid a foundation for endless disputes; but if he hopes to bring men by such a system to the knowledge of . . . the constitution, nature, signs, changes, and history of diseases . . . [he] takes much [the same] course with him that should walk up and down in a thick wood, overgrown with briars and thorns, with a design to take a view and draw a map of the country. (241)

4.    I thought the first step towards satisfying the several enquiries the mind of man was very apt to run into was to take a survey of our understandings, examine our own powers, and see to what things they are adapted. (I:i:7)

5.    [Idea] being that term which, I think, best serves to stand for whatsoever is the object of understanding when a man thinks, I have used it to express whatever is meant by phantasm, notion, species, or whatever it is which the mind can be employed about in thinking . . . (I:i:8)


  • Innate Ideas: e.g., God, Substance, Cause
    • Very general & abstract ideas
    • That could not arise from experience
    • Clearly & distinctly intellectually intuited 
    • Source of indubitable a priori knowledge about nature & reality.
  • Claimed innate knowledge claims are all either dubious or fatuous
    • dubious: conflicting rationalist claims about the nature and number of substances
    • fatuous: "What is is"; "The whole is greater than the part." {1}
  • We have no such clear and distinct understandings of various candidate ideas as rationalists maintain. {2}
  • Children & savages & the uneducated have no inking at all of any such abstract and general notions as these abstract ideas are supposed to be.
    • if an idea is in you you must be aware of it {3}
  • Leibniz's reply:
    • unconscious ideas are possible -- contra Locke & Descartes both
    • the issue is epistemological (what justifies claims to knowledge of necessary truths), not psychological (what suggests them to us).
  • It will clinch case against the innateness any presumed innate idea if
    • we can explain how the candidate ideas -- such as God -- arises from experience {4} {5}
    • or that we really have no such (clear and distinct) idea -- e.g. substance. {6}

1.    [Newton] demonstrated several propositions, which are so many new truths before unknown to the world, and are further advances in mathematical knowledge: but, for the discover of these it was not the general maxims "what is is"; or "the whole is bigger than a part," or the like that helped him. 

2.    [O]ur idea of sameness is not so settled and clear as to deserve to be thought innate in us. (I:ii:4)

3.    No proposition [or idea] can be said to be in the mind which it never yet knew, which it was never yet conscious of. (I:ii:5)

4.     It would suffice to convince unprejudiced readers of the falseness of this supposition [innate ideas] if I should only show . . . how men, barely by the use of their natural faculties, may attain to all the knowledge they have without the help of any innate impressions; and may arrive at certainty without any such original notions and or principles. (I:ii:1)

5.    And if they . . . carry the notion of excellency, greatness, or something extraordinary . . . the idea is likely to sink the deeper, and spread the farther; especially if it be an idea . . . naturally deducible from every part of our knowledge, as that of a God is. (I:ii:9)

6.     [W]e have no such clear idea at all, and therefore signify nothing by the word substance, but only an uncertain supposition of we know not what, i.e., of something whereof we have no particular and distinct positive idea, which we take to be the substratum, or support, or those ideas we do know. 

All Ideas

  • The mind, at birth, is a blank slate, a tabula rasa on which experience writes {1}
    • Outer experience: sensation: furnishes sensory qualities, e.g., yellow, white, heat, cold, soft, hard, bitter, sweet" {2}
    • Inner experience: reflection: furnishes "ideas which could not be had from things without," e.g., "perception, thinking, doubting, believing, reasoning, knowing, willing" {3}
  • Simple & Complex Ideas: by combining simple ideas (e.g., red, round, sweet) we form complex ones (e.g., cherry). {4}
    • Simple Ideas {5}
      • In things qualities which affect the senses are "united and blended" but they "enter by the senses simple and unmixed" {6}
      • Ideas deriving from sensation {7}
        • special sensibles:
          1. tastes (sweet), 
          2. feels (solid, smooth), 
          3. odors (floral), 
          4. sounds (dull thud),
          5. colors (yellow, white).
        • common sensibles: motion (still), shape (blocky), texture (smooth): can be both felt and seen
      • Ideas deriving from reflection {8}
        • thought or perception: e.g., remembering, discerning, reasoning, knowing, faith.
        • volition or willing: wishing, preferring, choosing, desiring
    • Complex ideas constructed from simple ones by various operations of the understanding {9}
      • union: this cherry
      • comparison: this cherry is sweeter than that apple
      • abstraction: by which the mind separates on idea from all those that accompany it: source of general ideas, {10} {11}
        • e.g. cherry:
          • abstract out, on tree (v. in bowl), 
          • Bing (v. Lady Ann), 
          • etc. 
        • e.g. whiteness
          • abstract out, the milk, the snow, the chalk, etc.
      • Compare: white and whiteness
        • this white simply an image
        • whiteness an complex abstraction from all the simple whites I've experienced
  • The Idea of Substance
    • Particular Sorts of Substances 
      • examples: man, horse | gold, water {12}
      • complex idea of = 
        • ideas of certain qualities or accidents +
        • obscure idea of substance or support +
        • idea of power: to cause & be affected
    • Our obscure idea of substance in general -- the substratum
      • bearer of properties:
      • "something I know not what" {13} {14}
        • what's extended <> extension
        • what thinks <> thought  {15}
    • Power

1.       Passive power or receptivity of change: from sensation: we observe the alterations of bodies 

2.       Active power or initiation of change: from reflection: from our experience of willing. {16}

3.       Element of necessity: the causal agent makes the patient change: the cause necessitates the effect: day always follows night, but fire causes heat {17}

1.     Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished? .... To this I answer in one word, from experience. (II:i:2)

2.     The great source of most of the ideas we have, depending wholly upon our senses, and derived by them to the understanding, I call sensation. (II:i:3)

3.     By reflection . . . I would be understood to mean that notice the mind takes of its own operation, and the manner of them. (II:i:4)

4.     The better to understand the nature, manner, and extent of our knowledge, one thing is carefully to be observed concerning the ideas that we have; and that is, that some of them are simple and some complex. (246)

5.     [T]here is nothing that can be plainer to a man than the clear and distinct perception he has of those simple ideas; which, being each in itself uncompounded, contains in it nothing but one uniform appearance or conception in the mind, and is not distinguishable into different ideas. (II:ii:1)

6.     [I]t is plain that the ideas that [perceived things] produce in the mind enter by the senses simple and unmixed. (II:ii:1)

7.     I would have anyone try to fancy any taste which had never affected his palate; or frame the idea of a scent he had never smelt: And when he can do this, I will also conclude that a blind man hath ideas of colours, and a deaf man true distinct notions of sounds. (II,ii,2)

8.     The two great and principle actions of the mind . . . that everyone who pleases may take notice of . . . in himself, are these two: perception or thinking; and volition or willing. (II:vi:2)

9.     When the understanding is once stored with these simple ideas it can, it has the power to repeat, compare, and unite them, . . .and so can make at pleasure new complex ideas. (II:ii,2)

10.   The use of words then being made to stand as outward marks of our internal ideas, and those ideas being taken from particular things, if every particular idea that we take in should have a distinct name, names must be endless. To prevent this, the mind makes the particular ideas received from the particular objects to become general; which is done by considering them as they are in the mind such appearances, separate from all other existences and the circumstances of real existence, as time, place, or any other concomitant ideas. This is called abstraction whereby ideas take from particular beings become general representatives of all of the same kind, and their names general names, applicable to whatever exists conformable to such abstract ideas. (II:xi:9)

11.   Thus the same colour, being observed today in chalk or snow, which the mind yesterday received from milk, it considers that appearance alone, makes it a representative of all that kind; and having given it the name whiteness, it by that sound signifies the same quantity wheresoever it be imagined or met with: And thus universals, whether terms or ideas, are made." (II:xi:9)

12.   It is the ordinary qualities observable in iron, or a diamond, put together, that make the true complex idea of those substances. (II:xxiii:3)

13.   If anyone should be asked what is the subject wherein colour or weight inheres, he would have nothing to say, but the solid extended parts; and if he were demanded, what is it that solidity and extension adhere in, he would not be in a much better case than the Indian . . . who saying that the world was supported by a great elephant, was asked what the elephant rested on; to which his answer was -- a great tortoise: but being again pressed to know what gave support to the broad-backed tortoise, replied -- something he knew not what. (II:xxiii:2)

14.   The idea . . . to which we give the general name substance [is] nothing but the supposed, but unknown, support of those qualities we find existing, which we imagine cannot exist sine re substante, without something to support them. (II:xxiii:2)

15.   [W]e have as clear a notion of the substance of spirit, as we have of body; the one being supposed to be (without knowing what it is) the substratum of those simple ideas we have from without; and the other supposed (with like ignorance of what it is) to be the substratum to those operations we experiment in ourselves within. (II:xxiii:5)

16.   The idea of a beginning of motion we have only from reflection on what passes in ourselves, where we find by experience that barely by willing it . . . we can move the parts of our bodies. (II:xxi: 4}

  1. The mind [takes] notice how one [thing] comes to an end, and ceases to be, and another begins to exist which was not before; . . . and [concludes] from what it has constantly observed to have been, that the like changes will for the future be made in the same things, by like agents, and by the like ways, . . . and so comes by that idea we call power.  (II:xxi:1)


  • Degrees of cognitive adequacy or knowledge
    • Certain
      • immediate certainty or intuition 
        • the mind immediately "sees" something to be: knowledge of own mind {1} and its contents: its ideas and their relations {9}
        • or be necessary, e.g., that nothing can come from nothing {2}
      • mediate certainty or demonstration 
        • the mind infers a necessary connection by a series of immediately "seen" steps.
        • knowledge of God's nature & existence {3}
    • Uncertain: sensation based "faith" or "opinion": based on experience or induction from experience: have probable assurance of these things or assurance sufficient for the guidance of action or practice.
      • external bodies {4}
      • other minds {5}
  • Ideas and Qualities {6}
    • Ideas: what the mind perceives in itself: e.g., the sensation of coldness, whiteness, roundness
    • Qualities: the power in the thing to produce these ideas in our minds: the whiteness, coldness, etc. of the snowball = its power to affect us in these ways.
  • Primary Qualities {7}
    • utterly inseparable from bodies
    • resemble the ideas they produce in us
    • short list: solidity, extension, figure, motion or rest, and number
  • Secondary Qualities {8}
    • nothing in the bodies themselves
    • don't resemble the ideas they produce
    • all the special sensible qualities of this nature

1.        [W]e have an intuitive knowledge of our own existence, and an internal infallible perception that we are (IV:ix:3) 

2.     In the next place, man knows, by an intuitive certainty, that bare nothing can no more produce any real being, than it can be equal to two right angles.  (IV:ix:3)

3.     If, therefore, there is some real being, and that nonentity cannot produce any real being, it is an evident demonstration, that from eternity there has been something . . . .  And that eternal being must be most powerful.  . . .  This eternal source, then, of all being must also be the source and original of all power; and so this eternal Being must be also the most powerful. . . .  And therefore God. (IV:x:6)

4.    [Regarding external existence] I have not that certainty of it that we strictly call knowledge; though the great likelihood of it puts me past doubt, and it be reasonable for me to do several things upon the confidence (IV:ix:9)

5.     And, therefore, though it be highly probable that millions of me do now exist, yet . . . I have not that certainty of it which we strictly call knowledge; though the great likelihood of it puts me past doubt, and it be reasonable for me to do several things upon the confidence that there are men . . . now in the world: but this is but probability, not knowledge. (IV:xi:9)

6.     Whatsoever the mind perceives in itself, or is the immediate object of perception, thought, or understanding, I call idea; and the power to produce any idea in our mind I call a quality of the subject wherein that power is. (II:viii:8)

7.     These I call original or primary qualities of bodies . . . solidity, extension, figure, motion or rest, and number. (II:viii:9)

8.     Secondly, such qualities which in truth are nothing in the objects themselves but powers to produce various sensations in us by their primary qualities, i.e., by the bulk, figure, texture, and motion of their insensible parts. (II:viii:10).

9.        It is the first act of the mind, when it has any sentiments or ideas at all, to perceive its ideas, and so far as it perceives them, to know each what it is, and thereby also to perceive their difference, and that one is not another.  . . .  By this the mind clearly and infallibly perceives each idea to agree with itself, and to be what it is; and all distinct ideas to disagree. (IV:i:4)

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