Hume’s Central PrinciplesHume’s Central Principles

Peter MillicanPeter Millican

Hertford College, OxfordHertford College, Oxford

3. Hume’s Logic: Relations, 3. Hume’s Logic: Relations, and Forms of Argumentand Forms of Argument

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The Heart of Hume’s PhilosophyThe Heart of Hume’s Philosophy

The core of Hume’s “Chief Argument” is in The core of Hume’s “Chief Argument” is in TreatiseTreatise Book 1 Part 3, the longest part of the Book 1 Part 3, the longest part of the entire entire TreatiseTreatise..

TreatiseTreatise 1.3 1.3 is entitled “Of Knowledge and is entitled “Of Knowledge and Probability”, however:Probability”, however:– Only Only T T 1.3.1 deals with “Knowledge” (a word 1.3.1 deals with “Knowledge” (a word

Hume uses in a strict sense, as meaning Hume uses in a strict sense, as meaning deductivedeductive knowledge). knowledge).

– Apart from the Apart from the titletitle of of T T 1.3.2, “probability” 1.3.2, “probability” doesn’t make an entrance until doesn’t make an entrance until T T 1.3.6.4.1.3.6.4.

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The Theme of CausationThe Theme of Causation

The real unifying theme of The real unifying theme of TreatiseTreatise 1.3 is 1.3 is causationcausation and causal reasoning. But and causal reasoning. But Hume’s route to his account is circuitousHume’s route to his account is circuitous!!

– He starts (in He starts (in TT 1.3.1-2) by 1.3.1-2) by developingdeveloping his his taxonomy of taxonomy of relations into a theory of relations into a theory of mental operations and of demonstrability;mental operations and of demonstrability;

– He then focuses on the relation of He then focuses on the relation of causation, seeking the key impression;causation, seeking the key impression;

– On the way to this, he discusses the On the way to this, he discusses the Causal Maxim, induction, probability …Causal Maxim, induction, probability …

3(a)3(a)

Hume’sHume’sTheory of Theory of RelationsRelations

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Introducing RelationsIntroducing RelationsHaving explained the association of ideas, Having explained the association of ideas, Hume calls it “a kind of ATTRACTION, which Hume calls it “a kind of ATTRACTION, which in the mental world” has remarkable effects in the mental world” has remarkable effects like gravity in the physical world (T 1.1.4.6).like gravity in the physical world (T 1.1.4.6).

One of these effects is to produce complex One of these effects is to produce complex ideas by uniting simples together; these “may ideas by uniting simples together; these “may be divided into RELATIONS, MODES, and be divided into RELATIONS, MODES, and SUBSTANCES” (SUBSTANCES” (TT 1.1.4.7). 1.1.4.7).

This provides a link into the main chapter on This provides a link into the main chapter on relations, relations, TT 1.1.5, though as we shall see, 1.1.5, though as we shall see,TT 1.3.1 is also very important. 1.3.1 is also very important.

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Natural and Philosophical RelationsNatural and Philosophical Relations

TT 1.1.5 starts with a distinction between two 1.1.5 starts with a distinction between two senses of the word “relation”. In one sense, senses of the word “relation”. In one sense, we think of things as we think of things as relatedrelated when the idea of when the idea of one one naturallynaturally leads the thought to the other. leads the thought to the other.

So the “natural relations” are those that So the “natural relations” are those that correspond to our associational tendencies – correspond to our associational tendencies – resemblance, contiguity, causation.resemblance, contiguity, causation.

But when philosophers talk about “relations”, But when philosophers talk about “relations”, they include they include any kind of arbitrary any kind of arbitrary “subject of “subject of comparison”. Hume develops Locke’s comparison”. Hume develops Locke’s taxonomy of such “philosophical relations”.taxonomy of such “philosophical relations”.

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Locke on the Types of Relation (1)Locke on the Types of Relation (1)

Locke (II xxv-xxviii) emphasises:Locke (II xxv-xxviii) emphasises:– ““Cause and Effect” (II xxvi 1‑2)Cause and Effect” (II xxvi 1‑2)– ““Relations of Time” (II xxvi 3‑4)Relations of Time” (II xxvi 3‑4)– ““Relations of Place and Extension” (II xxvi 5)Relations of Place and Extension” (II xxvi 5)– ““Identity and Diversity” (II xxvii)Identity and Diversity” (II xxvii)– ““Proportional Relations” (II xxviii 1)Proportional Relations” (II xxviii 1)

The last of these categories includes both The last of these categories includes both what Hume calls “degrees in quality” and what Hume calls “degrees in quality” and “proportions in quantity or number”“proportions in quantity or number”..

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Locke then says there are “infinite others” Locke then says there are “infinite others” of relations (II xxviii 1), notably:of relations (II xxviii 1), notably:– ““Natural RelationsNatural Relations” such as “” such as “FatherFather and and SonSon, ,

BrothersBrothers … … Country-menCountry-men” (II xxviii 2)” (II xxviii 2)– ““InstitutedInstituted, or , or VoluntaryVoluntary” relations such as ” relations such as

““GeneralGeneral …, …, CitizenCitizen, … , … PatronPatron and and ClientClient, … , … ConstableConstable, or , or DictatorDictator” (II xxviii 3)” (II xxviii 3)

– Various moral relations (II xxviii 4‑16)Various moral relations (II xxviii 4‑16)

Note that Locke does not mean the same Note that Locke does not mean the same by “natural relation” as Hume.by “natural relation” as Hume.

Locke on the Types of Relation (2)Locke on the Types of Relation (2)

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Locke’s “diversity” apparently becomes Locke’s “diversity” apparently becomes Hume’s “contrareity”.Hume’s “contrareity”.

Hume’s “resemblance” – which he says Hume’s “resemblance” – which he says enters into enters into allall relations – fulfils a similar role relations – fulfils a similar role to Locke’s ‘agreement’ (II xxviii 19).to Locke’s ‘agreement’ (II xxviii 19).

Locke doesn’t treat “resemblance” as a Locke doesn’t treat “resemblance” as a single type, but recognises myriad forms of single type, but recognises myriad forms of resemblance (e.g. “resemblance (e.g. “Country-menCountry-men, , i.e.i.e. those those who were born in the same Country”).who were born in the same Country”).

Locke to Hume on Relations (1)Locke to Hume on Relations (1)

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Hume seems deliberately to subsume Hume seems deliberately to subsume Locke’s “natural”, “instituted” and moral Locke’s “natural”, “instituted” and moral relations under cause and effect:relations under cause and effect:

“… “… all the relations of blood depend upon all the relations of blood depend upon cause and effect …” (cause and effect …” (TT 1.1.4.3) 1.1.4.3)

“… “… the relation of cause and effect … we may the relation of cause and effect … we may observe to be the source of all the relations of observe to be the source of all the relations of interest and duty, by which men influence each interest and duty, by which men influence each other in society, and are plac’d in the ties of other in society, and are plac’d in the ties of government and subordination.” (government and subordination.” (TT 1.1.4.5) 1.1.4.5)

Locke to Hume on Relations (2)Locke to Hume on Relations (2)

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Locke and Hume on RelationsLocke and Hume on Relations

[Locke doesn’t speak of [Locke doesn’t speak of “agreement” as a relation]“agreement” as a relation]

ResemblanceResemblance [a relation, but [a relation, but also involved in all relations]also involved in all relations]

Cause and effectCause and effect

Natural, Instituted, MoralNatural, Instituted, Moral

Cause and effectCause and effect

Relations of timeRelations of time

Relations of placeRelations of place

Space and timeSpace and time

IdentityIdentity IdentityIdentity

DiversityDiversity ContrarietyContrariety

Proportional relationsProportional relations Proportions in quantityProportions in quantity

Degrees in qualityDegrees in quality

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Hume’s DichotomyHume’s Dichotomy

Hume starts Hume starts TT 1.3.1 by dividing his seven 1.3.1 by dividing his seven types of relation into two groups types of relation into two groups (T(T 1.3.1.1) 1.3.1.1)::– The Four “Constant” RelationsThe Four “Constant” Relations

Those relations that “depend entirely on the Those relations that “depend entirely on the ideas, which we compare together” (i.e. ideas, which we compare together” (i.e. resemblanceresemblance, , contrarietycontrariety, , degrees in qualitydegrees in quality, , proportions in quantity or numberproportions in quantity or number););

– The Three “Inconstant” RelationsThe Three “Inconstant” RelationsThose relations that “may be chang’d without Those relations that “may be chang’d without any change in the ideas” (i.e. any change in the ideas” (i.e. identityidentity, , relations relations of time and placeof time and place, , cause and effectcause and effect).).

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A Taxonomy of Mental OperationsA Taxonomy of Mental Operations

Hume argues, rather simplistically, that his Hume argues, rather simplistically, that his seven relations map neatly onto four seven relations map neatly onto four different mental operations:different mental operations:– resemblanceresemblance, , contrarietycontrariety, and , and degrees in qualitydegrees in quality

are “discoverable at first sight” (are “discoverable at first sight” (TT 1.3.1.2) 1.3.1.2)– proportions of quantity or numberproportions of quantity or number are susceptible are susceptible

of demonstration (of demonstration (TT 1.3.1.2-5) 1.3.1.2-5)– identityidentity and and relations of time and placerelations of time and place are matters are matters

of perception rather than reasoning (of perception rather than reasoning (TT 1.3.2.1) 1.3.2.1)– causationcausation is the only relation “that can be trac’d is the only relation “that can be trac’d

beyond our senses, [to] existences and objects, beyond our senses, [to] existences and objects, which we do not see or feel” (which we do not see or feel” (TT 1.3.2.3) 1.3.2.3)

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Constant relationsConstant relations Inconstant relationsInconstant relations

PerceptionPerception IntuitionIntuition

resemblanceresemblance

contrarietycontrariety

degrees in qualitydegrees in quality

Sensory PerceptionSensory Perception

identityidentity

situations in timesituations in time and place and place

ReasoningReasoning DemonstrationDemonstration

proportions inproportions in quantity and number quantity and number

ProbabilityProbability

causationcausation

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Hume’s Dichotomy – the motiveHume’s Dichotomy – the motive

Hume gives his taxonomy of relations in Hume gives his taxonomy of relations in order to facilitate his arguments:order to facilitate his arguments:– That the Causal Maxim cannot be intuitively That the Causal Maxim cannot be intuitively

certain (certain (T T 1.3.3.2);1.3.3.2);– That relations of virtue and vice are not That relations of virtue and vice are not

demonstrable (demonstrable (T T 3.1.1.19).3.1.1.19).

He seems to argue from the principle:He seems to argue from the principle:– Any proposition that is intuitively or Any proposition that is intuitively or

demonstratively certain can contain only demonstratively certain can contain only constant relations.constant relations.

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The Failure of the Dichotomy The Failure of the Dichotomy

Sadly, this is nonsense. There are lots of Sadly, this is nonsense. There are lots of “analytic” propositions involving identity, “analytic” propositions involving identity, relations of time and place, or causation:relations of time and place, or causation:– If A=B and B=C, then A=C.If A=B and B=C, then A=C.– Anything that lies inside a small building lies Anything that lies inside a small building lies

inside a building.inside a building.– Every mother is a parentEvery mother is a parent..– Anyone whose paternal grandparents have Anyone whose paternal grandparents have

two sons, has an uncletwo sons, has an uncle..

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The Source of Hume’s Mistake?The Source of Hume’s Mistake?

I suggest that Hume confused, when I suggest that Hume confused, when considering propositions about objects:considering propositions about objects:– Supervenience: Supervenience: what is implied by what is implied by the the

propertiesproperties of the objects themselves of the objects themselves (independently of their relative situation etc.)(independently of their relative situation etc.)

– Analyticity: Analyticity: what is implied by what is implied by our ideasour ideas of the of the objects themselvesobjects themselves (independently of ideas (independently of ideas about their situation etc.)about their situation etc.)

(See Bennett 1971: 250‑6 and 2001: 242‑4 for (See Bennett 1971: 250‑6 and 2001: 242‑4 for the best published discussions of the issuethe best published discussions of the issue))

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Hume’s Conceivability PrincipleHume’s Conceivability Principle

Hume mostly relies not so much on his Hume mostly relies not so much on his Dichotomy as on the Dichotomy as on the Conceivability PrincipleConceivability Principle::

“’“’Tis an establish’d maxim in metaphysics, Tis an establish’d maxim in metaphysics, That whatever That whatever the mind clearly conceives includes the idea of possible the mind clearly conceives includes the idea of possible existenceexistence, or, in other words,, or, in other words, that nothing we imagine is that nothing we imagine is absolutely impossibleabsolutely impossible.” (.” (TT 1.2.2.8) 1.2.2.8)

““To form a clear idea of any thing, is an undeniable To form a clear idea of any thing, is an undeniable argument for its possibility, and is alone a refutation of any argument for its possibility, and is alone a refutation of any pretended demonstration against it.” (pretended demonstration against it.” (TT 1.3.6.5) 1.3.6.5)

““whatever we whatever we conceiveconceive is possible, at least in a is possible, at least in a metaphysical sense: but wherever a demonstration takes metaphysical sense: but wherever a demonstration takes place, the contrary is impossible, and implies a place, the contrary is impossible, and implies a contradiction.” (contradiction.” (AA 11, cf.  11, cf. EE 12.28) 12.28)

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Hume’s ForkHume’s Fork

In the In the EnquiryEnquiry, Hume replaces his D, Hume replaces his Dichotomy ichotomy with a distinction amongst propositionswith a distinction amongst propositions– Relations of IdeasRelations of Ideas can be known can be known a prioria priori – –

without any dependence on experience or real without any dependence on experience or real existenceexistence – – by inspecting ideas; hence their by inspecting ideas; hence their falsehood is inconceivable and they are falsehood is inconceivable and they are necessarily true.necessarily true.e.g.e.g. Pythagoras’ Theorem. (Pythagoras’ Theorem. (EE 4.1) 4.1)

3 3 × 5 = ½ × 30. (× 5 = ½ × 30. (EE 4.1) 4.1) All bachelors are unmarried.All bachelors are unmarried.

– The modern term is The modern term is analyticanalytic (as understood e.g. (as understood e.g. by Ayer): “true in virtue of its meaning”.by Ayer): “true in virtue of its meaning”.

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Matters of FactMatters of Fact

– Matters of FactMatters of Fact can’t be known can’t be known a prioria priori, and their , and their truth / falsity are equally conceivable:truth / falsity are equally conceivable:e.g.e.g. The sun will rise tomorrow. (The sun will rise tomorrow. (EE 4.2) 4.2)

The sun will not rise tomorrow. The sun will not rise tomorrow. ( (EE 4.2)4.2)

This pen will fall when released in air.This pen will fall when released in air.– Perhaps the closest modern term is Perhaps the closest modern term is syntheticsynthetic: a : a

proposition whose truth “is determined by the proposition whose truth “is determined by the facts of experience” (Ayer, facts of experience” (Ayer, LTLLTL 1971, p. 105). 1971, p. 105).

– But Hume (like Ayer) presumBut Hume (like Ayer) presumes that the es that the analytic/synthetic, a priori/a posteriori, and analytic/synthetic, a priori/a posteriori, and necessary/contingent distinctions all coincide.necessary/contingent distinctions all coincide.

3(b)3(b)

Hume onHume onForms of Forms of ArgumentArgument

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The Four “Kinds of Evidence”The Four “Kinds of Evidence”

Hume’s Hume’s Letter from a GentlemanLetter from a Gentleman (1745) (1745) explains some background to his explains some background to his TreatiseTreatise::

““It is common for Philosophers to distinguish the It is common for Philosophers to distinguish the Kinds of Evidence into Kinds of Evidence into intuitiveintuitive, , demonstrativedemonstrative, , sensiblesensible, and , and moral”moral”

““inintuition” means tuition” means self-evidenceself-evidence, “sensible” , “sensible” refers to refers to sensorysensory evidence evidence..

We have two forms of reasoning here, We have two forms of reasoning here, demonstrativedemonstrative, and “moral” or , and “moral” or probable probable reasoningreasoning..

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Demonstrative and ProbableDemonstrative and Probable

A Lockean distinction:A Lockean distinction:– In In demonstrativedemonstrative reasoning, each link in the reasoning, each link in the

inferential chain is “intuitively” certain (hence = inferential chain is “intuitively” certain (hence = “deductive” in the modern non-formal sense).“deductive” in the modern non-formal sense).

– In In probableprobable reasoning, some links are merely reasoning, some links are merely probable (hence = “inductive” in a loose sense).probable (hence = “inductive” in a loose sense).

Hume takes over Locke’s distinctionHume takes over Locke’s distinction– But in the But in the EnquiryEnquiry he also refers to he also refers to demonstrationdemonstration

as “reasoning concerning relations of ideas”,as “reasoning concerning relations of ideas”,

– and to and to probable reasoningprobable reasoning as “moral reasoning” or as “moral reasoning” or “reasoning concerning matter of fact”.“reasoning concerning matter of fact”.

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Probable/Factual InferenceProbable/Factual Inference

Consider:Consider: Mars is red and roundMars is red and round

thereforetherefore

Some round thing is colouredSome round thing is coloured

The premise and conclusion are matters of fact, The premise and conclusion are matters of fact, so is this “reasoning concerning matter of fact”?so is this “reasoning concerning matter of fact”?– Is the inference merely “probable”? No!Is the inference merely “probable”? No!– Does it go beyond “relations of ideas”? No!Does it go beyond “relations of ideas”? No!– Does justifying the inference require any appeal to Does justifying the inference require any appeal to

experience or to causal relations? No!experience or to causal relations? No!– Hence Hume would have to count it as Hence Hume would have to count it as demonstrativedemonstrative..

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Demonstration = Deduction?Demonstration = Deduction?

So deductive arguments – even those with So deductive arguments – even those with matter of fact premises and conclusions – matter of fact premises and conclusions – must count as “demonstrative” for Hume.must count as “demonstrative” for Hume.

But this is controversial, if view of passages But this is controversial, if view of passages such as the following:such as the following:– ““no matter of fact is capable of being no matter of fact is capable of being

demonstrated” (demonstrated” (T T 3.1.1.18);3.1.1.18);

– ““It seems to me, that the only objects of the It seems to me, that the only objects of the abstract sciences or of demonstration are quantity abstract sciences or of demonstration are quantity and number …” (and number …” (EE 12.27, cf.  12.27, cf. T 1.3.1.5T 1.3.1.5).).

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‘‘No Matter of Fact is Demonstrable’No Matter of Fact is Demonstrable’

Suppose I claim to Suppose I claim to demonstratedemonstrate that all that all crows are black.crows are black.– Ridiculous, you would say! How can I possibly Ridiculous, you would say! How can I possibly

demonstratedemonstrate such a contingent claim? such a contingent claim?

– ““Well”, I reply, “here’s my demonstration”:Well”, I reply, “here’s my demonstration”:

1. All crows are birds.1. All crows are birds.2. 2. All birds are black.All birds are black. All crows are black. All crows are black.

– That’s a demonstrative argument, isn’t it?That’s a demonstrative argument, isn’t it?

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What is Demonstrated?What is Demonstrated?

The crows argument is indeed The crows argument is indeed demonstrativedemonstrative, , but that isn’t enough to make it a but that isn’t enough to make it a demonstration demonstration ofof its conclusion. its conclusion.

To demonstrate To demonstrate Q from PQ from P is not the same as is not the same as demonstrating demonstrating Q tout courtQ tout court. The latter requires . The latter requires that the argument’s premises are known with that the argument’s premises are known with certainty to be true.certainty to be true.

Hume denies that any matter of fact can be Hume denies that any matter of fact can be demonstrateddemonstrated (tout court).(tout court). He nowhere denies He nowhere denies that one matter of fact can be demonstrated that one matter of fact can be demonstrated from anotherfrom another..

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Is Demonstrative Reasoning Is Demonstrative Reasoning Limited to Mathematics?Limited to Mathematics?

““There remain, therefore, algebra and arithemetic as the only There remain, therefore, algebra and arithemetic as the only sciences, in which we can carry on a chain of reasoning to sciences, in which we can carry on a chain of reasoning to any degree of intricacy, and yet preserve a perfect exactness any degree of intricacy, and yet preserve a perfect exactness and certainty.” (and certainty.” (TT 1.3.1.5) 1.3.1.5)

““It seems to me, that the only objects of the abstract sciences It seems to me, that the only objects of the abstract sciences or of demonstration are quantity and number …” (or of demonstration are quantity and number …” (EE 12.27) 12.27)

But Hume’s account of this limit is in terms of the But Hume’s account of this limit is in terms of the relative clarityrelative clarity of mathematical and moral ideas. of mathematical and moral ideas.

So if we want to find So if we want to find a posterioria posteriori demonstrative demonstrative arguments of any complexity, we have to look to arguments of any complexity, we have to look to appliedapplied mathematics … mathematics …

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Hume on Applied MathematicsHume on Applied Mathematics

Hume’s most explicit discussion of “mixed Hume’s most explicit discussion of “mixed mathematics” is in mathematics” is in EnquiryEnquiry Section IV: Section IV:

““it is a law of motion, discovered by experience, it is a law of motion, discovered by experience, that the moment or force of any body in motion is that the moment or force of any body in motion is in the compound ratio or proportion of its solid in the compound ratio or proportion of its solid contents and its velocity; and consequently, that contents and its velocity; and consequently, that a small force may remove the greatest obstacle a small force may remove the greatest obstacle … if, by any contrivance … we can encrease the … if, by any contrivance … we can encrease the velocity of that force, so as to make it an velocity of that force, so as to make it an overmatch for its antagonist.”overmatch for its antagonist.” ( (EE 4.13 4.13))

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The momentum of a body is equal to its mass The momentum of a body is equal to its mass multiplied by its velocity.multiplied by its velocity.

In any collision the total momentum of the colliding In any collision the total momentum of the colliding bodies (in any given direction) is conserved.bodies (in any given direction) is conserved.

2 kg25,000 m/s 4 m/s

10,000 kg

Before …

After …

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““Geometry assists us in the application of this Geometry assists us in the application of this law … but still the discovery of the law itself is law … but still the discovery of the law itself is owing merely to experience, and all the owing merely to experience, and all the abstract abstract reasoningsreasonings in the world could never lead us one in the world could never lead us one step towards the knowledge of it.” (step towards the knowledge of it.” (EE 4.13) 4.13)

““Mathematics, indeed, are useful in all Mathematics, indeed, are useful in all mechanical operations … But ’tis not of mechanical operations … But ’tis not of themselves they have any influence. … themselves they have any influence. … Abstract or demonstrative reasoningAbstract or demonstrative reasoning … never … never influences any of our actions, but only as it influences any of our actions, but only as it directs our judgment concerning causes and directs our judgment concerning causes and effects.” (effects.” (TT 2.3.3.2) 2.3.3.2)

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Demonstration = DeductionDemonstration = Deduction

Hume clearly Hume clearly doesdoes accept the possibility of accept the possibility of demonstrative argument in applied demonstrative argument in applied mathematics; hence he mathematics; hence he cannotcannot be be restricting demonstration to the restricting demonstration to the a prioria priori..

The natural interpretation of Humean The natural interpretation of Humean “demonstration” – especially in the light of “demonstration” – especially in the light of Hume’s Fork – is therefore “deduction” (in Hume’s Fork – is therefore “deduction” (in the informal sense: an argument whose the informal sense: an argument whose premises premises guaranteeguarantee its conclusion). its conclusion).

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Locke versus Hume onLocke versus Hume on“Probable Reasoning”“Probable Reasoning”

Although Hume follows Locke in taking for Although Hume follows Locke in taking for granted a general distinction between granted a general distinction between demonstrative [deductive] and probable demonstrative [deductive] and probable [inductive] reasoning, the two differ profoundly [inductive] reasoning, the two differ profoundly regarding the nature of the latter.regarding the nature of the latter.

Locke sees the operation of reasoning – both Locke sees the operation of reasoning – both demonstrative and probable – as involving the demonstrative and probable – as involving the perceptionperception of evidential connexions. of evidential connexions.

Hume denies any such perception in the case of Hume denies any such perception in the case of probable [inductive] inference.probable [inductive] inference.

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Locke on Reason as Locke on Reason as PerceptionPerception (1) (1)

““we … looke for noe greater certainty then what our we … looke for noe greater certainty then what our eyes can afford us, the whole evidence of this eyes can afford us, the whole evidence of this assureance being noe more then what the word assureance being noe more then what the word DemonstrationDemonstration doth naturaly import; which is to doth naturaly import; which is to shew any thing as it is & make it be perceived soe shew any thing as it is & make it be perceived soe that in truth what we come to know this way is not that in truth what we come to know this way is not by proofe but intuition, all the proofe that is used in by proofe but intuition, all the proofe that is used in this way of knowledg being noe thing else but this way of knowledg being noe thing else but shewing men how they shall see right … without shewing men how they shall see right … without useing arguments to perswade them that they are useing arguments to perswade them that they are soe”soe”

((Draft BDraft B of Locke’s of Locke’s Essay,Essay, 1671, p.153) 1671, p.153)

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Locke on Reason as Locke on Reason as PerceptionPerception (2) (2)

““InferenceInference … consists in nothing but the Perception of the … consists in nothing but the Perception of the connexion there is between the connexion there is between the IdeasIdeas, in each step of the , in each step of the deduction, whereby the Mind comes to see, either the deduction, whereby the Mind comes to see, either the certain Agreement of Disagreement of any two certain Agreement of Disagreement of any two IdeasIdeas, as , as in Demonstration, in which it arrives at Knowledge; or their in Demonstration, in which it arrives at Knowledge; or their probable connexion, on which it gives or with-holds its probable connexion, on which it gives or with-holds its Assent, as in Opinion. … For as Reason perceives the Assent, as in Opinion. … For as Reason perceives the necessary, and indubitable connexion of all the necessary, and indubitable connexion of all the IdeasIdeas or or Proofs one to another, in each step of any Demonstration Proofs one to another, in each step of any Demonstration that produces Knowledge; so it likewise perceives the that produces Knowledge; so it likewise perceives the probable connexion of all the probable connexion of all the IdeasIdeas or Proofs one to or Proofs one to another, in every step of a Discourse, to which it will think another, in every step of a Discourse, to which it will think Assent due. …” (Assent due. …” (EssayEssay IV xvii 2). IV xvii 2).

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““Nothing But a Species of Sensation”Nothing But a Species of Sensation”

Contrast Locke’s view of probable Contrast Locke’s view of probable reasoning with what Hume at reasoning with what Hume at TT 1.3.8.12: 1.3.8.12:

““Thus all probable reasoning is nothing but a Thus all probable reasoning is nothing but a species of sensation. ’Tis not solely in poetry and species of sensation. ’Tis not solely in poetry and music, we must follow our taste and sentiment, music, we must follow our taste and sentiment, but likewise in philosophy. When I am convinc’d but likewise in philosophy. When I am convinc’d of any principle, ’tis only an idea, which strikes of any principle, ’tis only an idea, which strikes more strongly upon me. When I give the more strongly upon me. When I give the preference to one set of arguments above preference to one set of arguments above another, I do nothing but decide from my feeling another, I do nothing but decide from my feeling concerning the superiority of their influence.”concerning the superiority of their influence.”