### Ideas from 'An Inquiry into Meaning and Truth' by Bertrand Russell [1940], by Theme Structure

#### [found in 'An Inquiry into Meaning and Truth' by Russell,Bertrand [Penguin 1967,-]].

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###### 3. Truth / A. Truth Problems / 7. Falsehood
 16477 Asserting not-p is saying p is false
 Full Idea: When you do what a logician would call 'asserting not-p', you are saying 'p is false'. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: This is presumably classical logic. If we could label p as 'undetermined' (a third truth value), then 'not-p' might equally mean 'undetermined'.
###### 4. Formal Logic / C. Predicate Calculus PC / 2. Tools of Predicate Calculus / e. Existential quantifier ∃
 16484 There are four experiences that lead us to talk of 'some' things
 Full Idea: Propositions about 'some' arise, in practice, in four ways: as generalisations of disjunctions; when an instance suggests compatibility of terms we thought incompatible; as steps to a generalisation; and in cases of imperfect memory. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: Modern logicians seem to have no interest in the question Russell is investigating here, but I love his attempt, however vague the result, to connect logic to real experience and thought.
###### 5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
 16486 The physical world doesn't need logic, but the mental world does
 Full Idea: The non-mental world can be completely described without the use of any logical word, …but when it comes to the mental world, there are facts which cannot be mentioned without the use of logical words. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: He adds that logical words are not needed for physics, but are needed for psychology. I love Russell's interest in the psychology of logic (in defiance of the anti-psychologism of Frege). See also the ideas of Robert Hanna.
###### 5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
 2947 Questions wouldn't lead anywhere without the law of excluded middle
 Full Idea: Without the law of excluded middle, we could not ask the questions that give rise to discoveries. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], c.p.88)
###### 5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / e. or
 16480 A disjunction expresses indecision
 Full Idea: A disjunction is the verbal expression of indecision, or, if a question, of the desire to reach a decision. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: Russell is fishing here for Grice's conversational implicature. If you want to assert a simple proposition, you don't introduce it into an irrelevant disjunction, because that would have a particular expressive purpose.
 16479 'Or' expresses hesitation, in a dog at a crossroads, or birds risking grabbing crumbs
 Full Idea: Psychologically, 'or' corresponds to a state of hesitation. A dog waits at a fork in the road, to see which way you are going. For crumbs on a windowsill, birds behave in a manner we would express by 'shall I be brave, or go hungry?'. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: I love two facts here - first, that Russell wants to link the connective to the psychology of experience, and second, that a great logician wants to connect his logic to the minds of animals.
 16481 'Or' expresses a mental state, not something about the world
 Full Idea: When we assert 'p or q' we are in a state which is derivative from two previous states, and we express this state, not something about the world. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: His example: at a junction this road or that road goes to Oxford, but the world only contains the roads, not some state of 'this or that road'. He doesn't deny that in one sense 'p or q' tells you something about the world.
 16487 Maybe the 'or' used to describe mental states is not the 'or' of logic
 Full Idea: It might be contended that, in describing what happens when a man believes 'p or q', the 'or' that we must use is not the same as the 'or' of logic. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: This seems to be the general verdict on Russell's enquiries in this chapter, but I love any attempt, however lacking in rigour etc., to connect formal logic to how we think, and thence to the world.
 16483 Disjunction may also arise in practice if there is imperfect memory.
 Full Idea: Another situation in which a disjunction may arise is practice is imperfect memory. 'Either Brown or Jones told me that'. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5)
###### 5. Theory of Logic / L. Paradox / 6. Paradoxes in Language / c. Grelling's paradox
 16475 A 'heterological' predicate can't be predicated of itself; so is 'heterological' heterological? Yes=no!
 Full Idea: A predicate is 'heterological' when it cannot be predicated of itself; thus 'long' is heterological because it is not a long word, but 'short' is homological. So is 'heterological' heterological? Either answer leads to a contradiction. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: [Grelling's Paradox] Yes: 'heterological' is heterological because it isn't heterological; No: it isn't, because it is. Russell says we therefore need a hierarchy of languages (types), and the word 'word' is outside the system.
###### 11. Knowledge Aims / A. Knowledge / 1. Knowledge
 16482 All our knowledge (if verbal) is general, because all sentences contain general words
 Full Idea: All our knowledge about the world, in so far as it is expressed in words, is more or less general, because every sentence contains at least one word that is not a proper name, and all such words are general. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: I really like this, especially because it addresses the excessive reliance of some essentialists on sortals, categories and natural kinds, instead of focusing on the actual physical essences of individual objects.
###### 11. Knowledge Aims / C. Knowing Reality / 1. Perceptual Realism / a. Naïve realism
 4758 Naïve realism leads to physics, but physics then shows that naïve realism is false
 Full Idea: Naïve realism leads to physics, and physics, if true, shows that naïve realism is false. Therefore naïve realism, if true, is false, therefore it is false. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], p.13) A reaction: I'm inclined to agree with this, though once you have gone off and explored representation and sense data you may be driven back to naïve realism again.
###### 12. Knowledge Sources / D. Empiricism / 1. Empiricism
 16476 For simple words, a single experience can show that they are true
 Full Idea: So long as a man avoids words which are condensed inductions (such as 'dog'), and confines himself to words that can describe a single experience, it is possible for a single experience to show that his words are true. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: One might question whether a line can be drawn between the inductive and the non-inductive in this way. I'm inclined just to say that the simpler the proposition the less room there is for error in confirming it.
###### 12. Knowledge Sources / D. Empiricism / 5. Empiricism Critique
 16485 Perception can't prove universal generalisations, so abandon them, or abandon empiricism?
 Full Idea: Propositions about 'some' may be proved empirically, but propositions about 'all' are difficult to know, and can't be proved unless such propositions are in the premisses. These aren't in perception, so forgo general propositions, or abandon empiricism? From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: This is obviously related to the difficulty empiricists have with induction. You could hardly persuade logicians to give up the universal quantifier, because it is needed in mathematics. Do we actually know any universal empirical truths?
###### 20. Action / C. Motives for Action / 3. Acting on Reason / b. Intellectualism
 16478 A mother cat is paralysed if equidistant between two needy kittens
 Full Idea: I once, to test the story of Buridan's Ass, put a cat exactly half-way between her two kittens, both too young to move: for a time she found the disjunction paralysing. From: Bertrand Russell (An Inquiry into Meaning and Truth [1940], 5) A reaction: Buridan's Ass is said to have starved between two equal piles of hay. Reason can't be the tie-breaker; reason obviously says 'choose one!', but intellectualism demands a reason for the one you choose.