Locke’s Essay Concerning Human Understanding—Book IV


     Copyright © 2015 Bruce W. Hauptli


Book IV. Of Knowledge and Opinion:


I am tempted to re-title this Book “Of Knowledge, Judgment, Faith, and Enthusiasm” since “opinion” is too broad a category.  As we shall see, his discussion of sensitive knowledge is meant to yield something “between” certain knowledge” and “mere opinion;” and his discussions of both “faith” and “enthusiasm” are extremely important to him. 


In this Book he will begin by characterizing what knowledge is; then discuss the types (or degrees) of knowledge; the extent of knowledge; our knowledge of self, a deity, and objects in the world); how we can improve our knowledge; and, finally, faith and enthusiasm. 


Chapter i. Of knowledge in general:


*IV i 2 Knowledge is the agreement and disagreement of ideas. 


-Critical Comment: exactly which agreements or disagreements of ideas is this claim a perception of?  The generalized version of this question is one which leaves many philosophical theories “hoist by their own petard[1]”—the theory of knowledge confronts the problem: Which ideas agree or disagree making this claim true? 


-Note that he does not define knowledge as “justified true belief” as do many epistemologists!  Given his “historical plain method,” the origin of ideas provides their foundational epistemological status (rather than some special “justificatory status”). 


*IV i 3 Such agreement/disagreement can be of four kinds: identity or diversity, relation, coexistence or necessary connection, and real existence. 


*-4. First, the mind clearly and infallibly perceives the identity and diversity of its ideas. 


*-5. Second, the mind perceives various relations between its ideas. 


*-6. Third, the mind perceives various of its ideas as [regularly] coexisting (or as not coexisting). 


*-7. Finally, Locke notes that another form of agreement or disagreement relevant to ideas is that of an “actual real existence” agreeing with an idea. 


--According to him, “within these four sorts of agreement or disagreement, is, I suppose, contained all the knowledge we have, or are capable of: for all the inquiries we can make, concerning any of our ideas, all that we know, or can affirm concerning any of them, is, that it is, or is no the same with some other; that it does, or does not always coexist with some other idea in the same subject; that it has this or that relation to some other idea; or that it has a real existence without the mind.” 


IV i 8 Locke distinguishes actual knowledge (which is the “present view the mind has of the agreement, or disagreement of any of its ideas”), and what he calls habitual knowledge (which is the memory of such agreement or disagreement).  While the latter can be as clear as the former, because it involves memory, it can also be inferior; and it is for this reason that what he will call “intuitive” knowledge is superior to what he calls “demonstrative” knowledge. 


Chapter ii. Of the degrees of our knowledge:


For Locke, the different “degrees” of knowledge arise from the different sorts of “perception” which we have of the disagreement (or disagreement) of our ideas.  Each of these could be considered to be a different (and praiseworthy) state of reflective consciousness. 


*IV ii 1 Intuitive knowledge is an immediate perception of the agreement or disagreement of our ideas.  It is both irresistible and certain. 


-If it seems odd to call “intuitive knowledge” perceptual, not that the “perception” in question is not sensory, it is a “perception of the mind”—a direct and immediate awareness of the “agreement or disagreement” of ideas (which may be perceptual, remembered, abstract, or general (and, thus, words).  One thing they can’t be, however, is innate. 


*IV ii 2 Demonstrative knowledge arises where the mind can not directly perceive the disagreement/disagreement of our ideas, but it may employ intermediate ideas [cf. IV ii 3] to perceive the agreements/disagreements.  Here we have reasoning, demonstration, and proof. 


-4. This sort of knowledge is certain, yet it is not as clear as intuitive knowledge: “this knowledge by intervening proofs, though it be certain, yet the evidence of it is not altogether so clear and bright, nor the assent so ready, as in intuitive knowledge.” 


-5. Before a demonstration, there is doubt regarding the agreement or disagreement of the ideas, but in the case of intuitive knowledge there is no such doubt. 


-7. Every step in a demonstration is intuitive! 


*-9. Demonstrative knowledge is not limited to the area of mathematics.  For example, we can have such knowledge in moral and social thought [cf., III xi 16, and IV iii 18: “where there is no property, there is no injustice,” and “no government allows absolute liberty”]. 


*IV ii 14 Sensitive knowledge, unlike intuitive and demonstrative, is not past doubting.  Strictly speaking, they alone are knowledge.  While it “comes short” of them, however:


-“there is, indeed, another perception of the mind, employed about the particular existence of finite beings without us; which going beyond bare probability, and yet not reaching perfectly to either of the foregoing degrees of certainty, passes under the name of knowledge.  There can be nothing more certain, than that the idea we receive from an external object is in our minds; this is intuitive knowledge.  But whether there be anything more than barely that idea in our minds; whether we can thence certainly infer the existence of anything without us, which corresponds to that idea, because men may have such ideas in their minds when no such thing exists, no such object affects their senses.  But yet here, I think, we are provided with an evidence, that puts us past doubting; for I ask anyone, whether he looks on the sun by day, and thinks on it by night; when he actually tastes wormwood, or smells a rose, or only thinks on that savor, or odor?  We as plainly find the difference there is between any idea received in our minds by our memory, and actually coming into our mind by our senses, as we do between any two distinct ideas. 


--We need to look very carefully at this passage.  Reflecting back to IV I 2, we don’t seem to have here “perceptions of relations of ideas”—the “relation” here seems to be one between ideas and things!  Nonetheless he uses perception here!  On the one hand, we need to contrast and compare “sensitive knowledge” with “intuitive” and “demonstrative” knowledge.  On the other hand, we need to contrast “sensitive knowledge” with “judgment” [IV vi 13]! 


Chapter iii. Of the extent of human knowledge:


IV iii 1 Our knowledge extends no further than our ideas! 


IV iii 2 Our knowledge extends no further than our ability to perceive the agreement or disagreement of our ideas. 


IV iii 3 We can not relate all of our ideas directly to our other ideas (that is, intuitive knowledge is limited to our ability to directly perceive agreements and disagreements of our ideas). 


IV iii 4 We can have demonstrative knowledge only where we can find intermediate ideas (mediums).  Cf., IV iii 18. 


IV iii 5 Our sensitive knowledge is limited to what we can experience. 


-But see his discussion of microscopes at II xxiii 11.  While he says he relies on “sensory” experience, he is clearly willing to “go beyond” “bare, naked perception!” 


IV iii 8 Our knowledge of the identity and diversity of ideas extends to all of our ideas. 


IV iii 9 Our knowledge of the coexistence of various ideas has a much smaller span. 


-10. We have no idea at all of what “connects” the coexisting simple ideas together. 


-12. We have no idea what connects primary and secondary qualities together. 


-14. We are limited to our [sensory] experience in regard to knowledge of substances (coexisting ideas). 


-Gold example (p. 241). 


-16. In regard to bodies, the “corpuscularian hypothesis” may well be the best that we can do. 


-17. We are even more in the dark in regard to knowledge of “spirits.” 


IV iii 18 Our knowledge of other relations of our ideas (beyond identity, diversity, and coexistence) is limited to our ability to find “intermediate ideas, that may show the relations and habitues of ideas, whose coexistence is not considered....”


-From ideas of a deity and of a person, we can demonstrate moral claims (perceive the moral relationship of certain ideas through intermediate ideas): for example: “where there is no property, there is no injustice,” and “no government allows absolute liberty.”  These claims show that Locke believes that demonstrative knowledge is not limited to mathematics (cf., IV ii 9). 


-19. Both their complexity and the absence of sensible representations make moral demonstrations difficult. 


IV iii 21 Our knowledge of real existences depends upon the sort of existent:


-we have intuitive knowledge of ourselves (cf., IV ix);

-we have demonstrative knowledge of a deity (cf., IV x); and

-we have sensitive knowledge of [some] other things (cf., IV xi). 


-22. Our “want” of knowledge here is explained by the absence of ideas, by the absence of discoverable connections between our ideas, and by the difficulty of tracing and examining the ideas we do have. 


*-23-26. Our “scientific knowledge” [IV iii 26] of “physical things” will be limited, and we will have to settle for “experimental philosophical knowledge” of them [IV iii 26].  In addition, we are limited to those things out of the totality of things in the universe which we may experience (and remote, large, or small things may be “beyond” our experience). 


--Clearly, we must recognize that Locke uses ‘science’ to denote those areas where we have full knowledge (which must be certain).  What he calls “experimental philosophical knowledge of things” is what we now call “science.” 


Chapter iv. Of the reality of knowledge:


*IV iv 1 Locke recognizes that the following question confronts his orientation: “if it be true, that all knowledge lies only in the perception of agreement and disagreement of our own ideas, the visions of an enthusiast [cf., IV xix], and the reasonings of a sober man, will be equally certain.”  That is, the Lockean empiricist confronts a basic skeptical challenge, and Locke wishes to meet it (showing that his view doesn’t amount to constructing “castles in the air”). 


-Cf., and contrast: IV xviii and xix. 


-2. To limit our knowledge simply to our ideas would be to render it useless.  This claim needs to be kept in mind as you turn to reading Berkeley! 


*IV iv 3 “‘Tis evident, the mind knows not things immediately, but only by the intervention of the ideas it has of them.  Our knowledge therefore is real, only so far as there is a conformity between our ideas and the reality of things.  But what shall be here the criterion [of such conformity]? 


-Here we are confronted with two important aspects of Locke’s thought (they have been in the background throughout the text): his claim that what we experience are ideas, and his commitment to a representational theory of truth.  These, of course, immediately yield the skeptical challenge which began this chapter.  If either of these Lockean theses is denied, the problem is dissolved (or at least it is transformed).  For example, if one contends that we directly experience things, then one can avoid skepticism.  On the other hand, if one holds that we experience ideas but that truth is a relationship between ideas (saying, for example, that where ideas correctly, or fruitfully, stand as signs for, or predictors of, other subsequent ideas, then they are true), again the skeptical problem disappears.  The former move is made by Thomas Reid (a Scottish philosopher who lived from 1710-1796), while the latter move is made by George Berkeley (an Irish philosopher who lived from 1685-1753). 


--Richard Rorty characterizes quite well Locke’s problem with representationalism when he says: “whereas Aristotle had not had to worry about an Eye of the Mind, believing knowledge to be the identity of the mind with the object known, Locke did not have this alternative available.  Since for him impressions were representations, he needed a faculty which was aware of the representations, a faculty which judged the representation rather than merely had them—judged that they existed, or that they were reliable, or that they had such-and-such relations to other representations.  But he had no room for one, for to postulate such a faculty would have intruded a ghost into the quasi-machine whose operations he hoped to describe.  He kept just enough of Aristotle to retain the idea of knowledge as consisting of something object-like entering the soul, but not enough to avoid either skeptical problems about the accuracy of representations or Kantian questions about the difference between intuitions with and without the “I think.”  To put it another way, the Cartesian conglomerate mind which Locke took for granted resembled Aristotelian...[concept] just enough to give a traditional flavor to the notion of “impression” and departed from it just enough to make Humean skepticism and Kantian transcendentalism possible.  Locke was balancing awkwardly between knowledge-as-identity-with-object and knowledge-as-true-judgment-about-object, and the confused idea of “moral philosophy” as an empirical “science of man” was possible only because of this transitional stance.”[2] 


-4. Our knowledge of simple ideas, of course, is real knowledge: since the mind can not make them, they “...must necessarily be the product of things operating on the mind in a natural way, and producing therein those perceptions....” 


-5-6. Our knowledge of complex ideas which are not of substances is real knowledge also, because they are archetypes which are not intended to be copies (in effect, then, they are the “zero case” of representational knowledge).  Mathematical knowledge is an example here. 


IV iv 8 For real knowledge both distinct ideas and correspondence to archetypes are necessary. 


-12. To have real knowledge of substances, then, we would have to have more than consistent sets of coexisting simple ideas.  Thus “...the reality of our knowledge concerning substances, [is] that all our complex ideas of them must be such...as are made up of such simple ones, as have been discovered to coexist in nature.” 


Chapter v. Of truth in general: [skip]


IV v 1 Truth, for Locke, is the joining of signs so that the “corresponding things” agree. 


IV v 5 He holds that there are two sorts of propositions:


-mental propositions, (where ideas are put together without words) and


-verbal propositions (where words are employed). 


Chapter vi. Of universal propositions, their truth and certainty:


In my "re-titling" of Book IV, we now move to the second major topic: judgment [knowledge, judgment, faith, and enthusiasm]


IV vi 4 If we are to know the truth of any general propositions, the must have precise knowledge of the essences of the various species or sortals involved. 


-11. “The qualities which make our complex idea of substances, depend mostly on external, remote, and unperceived causes.” 


*IV vi 13 Locke maintains that we can have what he calls “judgment:” “possibly inquisitive and observing men may, by strength of judgment, penetrate farther, and on probabilities taken from wary observation, and hints well laid together, often guess right at what experience has not yet discovered to them.  But this is but guessing still; it amounts only to opinion, and has not that certainty, which is requisite to knowledge.  For all general knowledge lies only in our own thoughts, and consists barely in the contemplation of our own abstract ideas....” 


-Cf., IV xiv 3: there he defines judgment as a process “...whereby the mind takes its ideas to agree, or disagree; or which is the same, any proposition to be true, or false, without perceiving a demonstrative evidence in the proofs.” 


-We need to compare and contrast what he says about “judgment” with what he says about “sensitive knowledge” [IV ii 14]! 


Chapter vii. Of maxims: [skip]


Chapter viii. Of trifling propositions: [skip]


Chapter ix. Of our knowledge of existence:


In Chapters IX-XI, Locke discusses our knowledge of ourselves, a deity, and “things in the world.”  Here he is answering several of the central questions he has set for the book regarding the nature and extent of our knowledge.  We have already seen what sorts of knowledge there are (intuitive, demonstrative, and sensitive), and we have seen what our knowledge of ideas amounts to.  We now turn to our knowledge of “things” generally construed. 


*IV ix 3. “As for our own existence, we perceive it so plainly, and so certainly, that it neither needs, nor is capable of any proof.  For nothing can be more evident to us, than our own existence.  I think, I reason, I feel pleasure and pain; can any of these be more evident to me, than my own existence?  If I doubt of all other things, that very doubt makes me perceive my own existence, and will not suffer me to doubt of that.  For if I know I feel pain, it is evident, I have as certain a perception of my own existence, as of the existence of the pain I feel: or if I know I doubt, I have as certain a perception of the existence of the thing doubting, as of that thought, which I call doubt.  Experience then convinces us, that we have an intuitive knowledge of our own existence, and an internal infallible perception that we are.  In every act of sensation, reasoning or thinking, we are conscious to ourselves of our own being; and, in this matter, come not short of the highest degree of certainty.” 


-Cf., IV x 2! 


-Note the difference between Locke’s argument here and Descartes’ cogito argument! 


-Critical Comment: here he argues that we have intuitive knowledge of the self.  But he also contends that we have knowledge only of the agreement and disagreement of ideas.  Moreover, for knowledge to be intuitive, the ideas in question must be clear and distinct.  But it is certainly questionable, especially given his extended discussion of personal identity, that we have a clear and distinct idea of the self.  Indeed, it is questionable whether we have an idea of the self at all.  Finally, and most centrally, the self is not an idea, and thus it is not clear that we can have knowledge of it. 


-In his A History of Western Philosophy: Philosophy From the Renaissance to the Romantic Age, A. Robert Caponigri maintains that: “Locke believes that we do possess such an apprehension [of “real existence”—that is, things, rather than ideas] or perception.  It is the perception which the conscious subject has of itself.  This perception renders the subject present to itself as a real existent, and may therefore, presumably form the point of departure of the kind of knowledge and proof we are seeking.”[3]  He continues, noting that “the judgment [here] of existence, however, has certain features of its own.  As a matter of fact, this judgment, in the case of the subject’s own existence is unique.  The only other judgment having any similarity to it is that concerning the existence of God.  The uniqueness of this judgment resides in the fact that in it not only the ideas, but the mind itself, is present to the understanding.  No idea or sign of any kind is needed to represent the mind.  It is not as a “tertium quid,”[4] but as the very substance and actuality of the entire process.  This unique knowledge of the subject’s own existence becomes, however, the basis and the model for the knowledge of other orders of real existences.”[5] 


Chapter x. Of our knowledge of the existence of a GOD:


*IV x 1 Though we have no innate idea of a deity, we can prove the existence of a deity through experience. 


*IV x 3 We know through intuitive certainty that “bare nothing can no more produce any real being, than it can be equal to two right angles.” 


-Cf., IV x 8. 


-Note that some hold such truths to be a priori ones.  Can Locke maintain this?  Even his intuitive claims have a “perceptual basis,” and all demonstrations must consist of a series of intuitions!  In general, empiricists who follow Locke have difficulty accounting for a priori truths or knowledge! 


-“If therefore we know there is some real being, and that non-entity cannot produce any real being, it is an evident demonstration, that from eternity there has been something; since what was not from eternity, had a beginning; and what had a beginning, must be produced by something else.” 


In his Locke: His Philosophical Thought, Nicholas Jolley maintains that:


…like many other traditional proofs of the existence of God, Locke’s proof relies on the supposedly a priori principle that something cannot come from nothing.  Locke deploys this principle as early as the first stage of the argument to prove the principle of an eternal being.  To this principle he adds a premise which has a better claim to intuitive certainty; with a clear echo of Descartes’s cogito egro sum Locke remarks that he certainly knows the existence of at least one being, namely himself.  From these premises Locke seeks to infer the conclusion that an eternal being exists.  For if some thing such as himself exists, then either it is eternal or it has a beginning in time; if it has a beginning in time, then by the causal principle it owes its existence to something else external.  The same argument can them be run with respect to this further being, and so on, until we are led to the conclusion that an eternal being exists. 

  Since Leibniz critics have been quick to complain that this argument involves an egregious instance of the fallacy of equivocation, and unfortunately this criticism appears to be justified.  Locke states the conclusion of his argument in the form: “From eternity there has been something:…but he appears not to see that this sentence is ambiguous between: (1) There has never been a time when nothing existed; and (2) Some one thing has always existed.  Obviously (2) does not follow from (1), but though Locke clearly intends to assert the stronger (2), he is entitled only to the weaker (1).  His argument shows at most that there must be a series of finite beings which extends backwards to infinity in time.[6] 


*IV x 4 This eternal thing must be most powerful. 


*IV x 5 This eternal thing must be most knowing. 


-Cf., IV x 10, where Locke argues that an “incognitive thing” could not cause a cognitive thing. 


*IV x 6 Therefore God exists: “thus from the consideration of ourselves, and what we infallibly find in our constitutions, our reason leads us to the knowledge of this certain and evident truth, that there is an eternal, most powerful, and most knowing being; which whether anyone will please to call God, it matters not.” 


-Note that this is not an ontological argument for the existence of a deity—it is based upon experience.  Contrast Locke and the Continental Rationalists here. 


IV x 14-19 This eternal thing can’t be material—the cognitive must come from the cognitive. 


Chapter xi. Of our knowledge of the existence of other things:


*IV xi 1 “The knowledge of the existence of any other thing, we can have only by sensation: for there being no necessary connection of real existence, with any idea a man has in his memory, nor any other existence but that of GOD, with the existence of any particular man; no particular man can know the existence of any other being, but only when by actual operating upon him, it makes itself perceived by him.  For the having the idea of anything in our mind, no more proves the existence of that thing, than the picture of a man evidences his being in the world, or the visions of a dream make thereby a true history.” 


-2. For example, the whiteness of this paper: “’Tis therefore the actual receiving of ideas from without, that gives us notice of the existence of other things, and makes us know, that something does exist at that time without us, which causes that idea in us, though perhaps we neither know nor consider how it does it....” 


*-3. Our knowledge here is not as certain as that arrived at in intuition or demonstration, “...yet it is an assurance that deserves the name of knowledge.  If we persuade ourselves that our faculties act and inform us right, concerning the existence of those objects that affect them, it cannot pass for an ill-grounded confidence: for I think nobody can, in earnest, be so skeptical, as to be uncertain of the existence of those things which he sees and feels.” 


--“This is certain, the confidence that our faculties do not herein deceive us, is the greatest assurance we are capable of, concerning the existence of material beings.” 


-5. The sensory ideas come unbidden, and are unavoidable.  There is a manifest difference between them and remembered ideas (in terms of their clarity and distinctness). 


*-8. To those who are skeptical here he replies: (i) the very skeptical question would, then, be a dream; (ii) while the “certainty” we have here is not as great as we can attain to (in intuition and demonstration), “...it is [as great] as our condition needs.”  It is sufficient to govern our conduct in the world. 


--“...this evidence is as great, as we can desire, being as certain to us, as our pleasure or pain, i.e. happiness or misery; beyond which we have no concernment, either of knowing or being.  Such an assurance of the existence of things without us, is sufficient to direct us in the attaining the good and avoiding the evil, which is caused by them, which is the important concernment we have of being made acquainted with them.” 


IV xi 11 Knowledge of past existences is had through memory. 


Chapter xii. Of the improvement of our knowledge:


IV xii 1 Locke indicates that it is not through maxims (or abstract principles) that we achieve knowledge. 


IV xii 3 According to him, particular truths are known first, and general maxims are learned later through abstraction. 


-Cf., IV xii 7. 


IV xii 4 He contends that principles which are not carefully examined (and “reduced” to their atomic constituents) are dangerous and misleading. 


IV xii 9 He contends that our knowledge of bodies is to be improved only through experience: “...we can go no farther than the simple ideas of our nominal essence will carry us, which is very little beyond themselves; and so afford us but very sparingly any certain, universal, and useful truth.” 


-10. These improvements will not yield certainty, but they will constitute an advance: “I deny not, but a man accustomed to rational and regular experiments shall be able to see farther into the nature of bodies, and guess righter at their yet unknown properties, than one, that is a stranger to them: but yet, as I have said, this is but judgment and opinion, not knowledge and certainty.  This way of getting and improving our knowledge in substances only by experience and history, which is all that the weakness of our faculties in this state of mediocrity, which we are all in in this world, can attain to, makes me suspect, that natural philosophy is not capable of being made into science…. Experiments and historical observations we may have, from which we may draw advantages of ease and health, and thereby increase our stock of conveniences for this life: but beyond this, I fear our talents reach not, nor are our faculties, as I guess, able to advance. 


-11. “...our proper employment lies in those inquiries, and in that sort of knowledge, which is most suited to our natural capacities, and carries in it our greatest interest, i.e. the condition of our eternal estate.  Hence I think I may conclude, that morality is the proper science, and business of mankind in general....” 


IV xii 13-14 Hypotheses have their place, but only the perception of clear and distinct agreements and disagreements of ideas yields knowledge (properly so-called). 


Chapter xiii. Some further considerations concerning our knowledge: [skip]


Chapter xiv. Of judgment:


*IV xiv 1 Our knowledge (properly so-called) is too limited for life!  An individual who awaited certainty would “...not eat, till he has demonstration that it will nourish him; he...will not stir, ‘till he infallibly knows the business he goes about will succeed; will have little else to do, but sit still and perish.” 


*IV xiv 3 Here the importance of judgment arises.  It is defined as a process “...whereby the mind takes its ideas to agree, or disagree; or which is the same, any proposition to be true, or false, without perceiving a demonstrative evidence in the proofs.” 


-IV xiv 4 It is a presuming of things to be so, without the perception that this is the case. 


Chapter xv. Of probability:


IV xv 1 Locke defined “probability” as “the appearance of agreement upon fallible proofs:”


-IV xv 3 He notes that there is no “intuition” here as there is in the case of intuitive and demonstrative knowledge. 


-IV xv 4 He notes that there are two grounds for such “judgments:” conformity with our experience, and the testimony of others’ experience. 


Chapter xvi. Of the degrees of assent: [skip]


Chapter xvii. Of reason: [skip]


IV xvii 24 Here Locke maintains that it is our duty as rational creatures to have our beliefs conform to our evidence—normativity enters epistemology in terms of our responsibility to ensure that our beliefs have adequate, positive, empirical evidence. 

Chapter xviii. Of faith and reason, and their distinct provinces:


In my "re-titling" of Book IV, we now move to the third major topic: faith [knowledge, judgment, faith and enthusiasm

In effect we might say that Locke contends that we have three sorts of grounds for assent:


reason (with, presumably four sub-varieties: intuitive, demonstrative, and sensitive knowledge, as well as judgment),


faith, and




Of course, there is a gigantic difference between these “grounds,” and while the former is good, the latter is bad! 


IV xviii 2 Locke distinguishes reason and faith.  The latter is characterized by revelation rather than grounds or proof. 


-IV xviii 3 According to Locke, no simple idea can be provided by revelation. 


-IV xviii 5-10 According to him, revelation can not be admitted when it conflicts with the clear evidence of reason. 


--7. Some things are beyond our reason—we can only assent to them via faith. 


--10. “Whatever GOD has revealed, is certainly true; no doubt can be made of it.  This is the proper object of faith; but whether it be a divine revelation, or no, reason must judge; which can never permit the mind to reject a greater evidence to embrace what is less evident, nor allow it to entertain probability in opposition to knowledge and certainty.  There can be no evidence, that any traditional revelation is of divine original, in the words we receive it, and in the sense we understand it, so clear, and so certain, as those of the principles of reason; and therefore, nothing that is contrary to, and inconsistent with the clear and self-evident dictates of reason, has a right to be urged, or assented to, as a matter of faith, wherein reason has nothing to do.  Whatsoever is divine revelation, ought to over-rule our opinions, prejudices, and interests, and has a right to be received with a full assent: such a submission as this of our reason to faith, takes not away from the landmarks of knowledge: this shakes not the foundations of reason, but leaves us that use of our faculties, for which they were given us.” 


[Chapter xix. Of enthusiasm]


In my "re-titling" of Book IV, we now move to the fourth major topic: enthusiasm [knowledge, judgment, faith, and enthusiasm]


Our editor has not included any selections from this section, but an electronic copy of this chapter is available and I recommend reading it.  Locke wants to note that enthusiasm is what too many people use as a “ground” for their beliefs.  Of course he doesn’t think much of this “ground.”  


10. “How do I know that God is the revealer of this to me; that this impression is made upon my mind by his Holy Spirit; and that therefore I ought to obey it?  If I know not this, how great soever the assurance is that I am possessed with, it is groundless; whatever light I pretend to, it is but enthusiasm.” 


14. “He therefore that will not give himself up to all the Extravagancies of Delusion and Error must bring this Guide of his Light within to the Tryal.  God when he makes the Prophet does not unmake the Man.  He leaves all his Faculties in their natural State, to enable him to judge of his Inspirations, whether they be of divine Original or no.  When he illuminates the Mind with supernatural Light, he does not extinguish that which is natural.  If he would have us assent to the Truth of any Proposition, he either evidences that Truth by the usual Methods of natural Reason, or else makes it known to be a Truth, which he would have us assent to, by his Authority, and convinces us that it is from him, by some Marks which Reason cannot be mistaken in.  Reason must be our last Judge and Guide in every Thing.  I do not mean, that we must consult reason, and examine whether a Proposition revealed from God can be made out by natural Principles, and if it cannot, that then we may reject it: But consult it we must, and by it examine, whether it be a Revelation from God or no: And if Reason finds it to be revealed from God, Reason then declares for it, as much as for any other Truth, and makes it one of her Dictates.” 


Chapter xx. Of wrong assent or error: [skip]


Chapter xxi. Of division of the sciences: [skip]




Notes: [click on note number to return to text for that note]

[1] A petard was a small bomb used to blow up gates and walls in attempts to breach fortifications—to be blown up by one’s own bomb is the underlying metaphor here (the philosophical theory is to be “universal,” but when it is applied to itself it “explodes.” 

[2] Richard Rorty, Philosophy and the Mirror of Nature, op. cit., pp. 144. 

[3] A. Robert Caponigri, A History of Western Philosophy: Philosophy From the Renaissance to the Romantic Age (Notre Dame: Univ. of Notre Dame, 1963), p. 309. 

[4] A tertium quid is a “third something”—an indefinite or undefined thing related in some way to two definite or known things (that is, a mediating factor). 

[5] A. Robert Caponigri, A History of Western Philosophy: Philosophy From the Renaissance to the Romantic Age, op. cit., p. 309. 

[6] Nicholas Jolley, Locke: His Philosophical Thought (Oxford: Oxford U.P., 1999), pp. 96-97. 

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