100 ideas
| 22659 | It is wisdom to believe what you desire, because belief is needed to achieve it [James] |
| Full Idea: Clearly it is often the part of wisdom to believe what one desires; for the belief is one of indispensable preliminary conditions of the realisation of its object. | |
| From: William James (The Sentiment of Rationality [1882], p.43) | |
| A reaction: Roughly, action is impossible without optimism about possible success. This may count as instinct, rather than 'wisdom'. |
| 22657 | All good philosophers start from a dumb conviction about which truths can be revealed [James] |
| Full Idea: Every philosopher whose initiative counts for anything in the evolution of thought has taken his stand on a sort of dumb conviction that the truth must lie in one direction rather than another, and a preliminary assurance that this can be made to work. | |
| From: William James (The Sentiment of Rationality [1882], p.40) | |
| A reaction: I would refer to this as 'intuition', which I think of as reasons (probably good reasons) which cannot yet be articulated. Hence I like this idea very much, except for the word 'dumb'. It is more like a rational vision, yet to be filled in. |
| 22647 | A complete system is just a classification of the whole world's ingredients [James] |
| Full Idea: A completed theoretic philosophy can never be anything more than a completed classification of the world's ingredients. | |
| From: William James (The Sentiment of Rationality [1882], p.23) | |
| A reaction: I assume this is not just the physical ingredients, but must also include our conceptual scheme - but then we must first decide which is the best conceptual scheme to classify, and that's where the real action is. [He scorns such classifation later]. |
| 22648 | A single explanation must have a single point of view [James] |
| Full Idea: A single explanation of a fact only explains it from a single point of view. | |
| From: William James (The Sentiment of Rationality [1882], p.23) | |
| A reaction: I take this to imply that multiple viewpoints lead us towards objectivity. The single viewpoint of an expert is of much greater value than that of a novice, on the whole. |
| 22642 | Man has an intense natural interest in the consistency of his own thinking [James] |
| Full Idea: After man's interest in breathing freely, the greatest of all his interests (because it never fluctuates or remits….) is his interest in consistency, in feeling that what he now thinks goes with what he thinks on other occasions. | |
| From: William James (The Pragmatist Account of Truth [1908], 'Seventh') | |
| A reaction: People notoriously contradict themselves all the time, but I suspect that it is when they get out of their depth in complexities such as politics. They probably achieve great consistency within their own expertise, and in common knowledge. |
| 22644 | Our greatest pleasure is the economy of reducing chaotic facts to one single fact [James] |
| Full Idea: Our pleasure at finding that a chaos of facts is the expression of single underlying fact is like a musician's relief at discovering harmony. …The passion for economy of means in thought is the philosophic passion par excellence. | |
| From: William James (The Sentiment of Rationality [1882], p.21) | |
| A reaction: We do, though, possess an inner klaxon warning against stupid simplistic reductions. Reducing all the miseries of life to the workings of the Devil is not satisfactory, even it it is economical. Simplicities are dangerously tempting. |
| 6710 | You can only define a statement that something is 'true' by referring to its functional possibilities [James] |
| Full Idea: Pragmatism insists that statements and beliefs are inertly and statically true only by courtesy: they practically pass for true; but you cannot define what you mean by calling them true without referring to their functional possibilities. | |
| From: William James (The Meaning of the Word "Truth" [1907], p.2) | |
| A reaction: I think this clarifies an objection to pragmatism, because all functional definitions (e.g. of the mind, or of moral behaviour) are preceded by the question of WHY this thing is able to function in this way. What special quality makes this possible? |
| 18986 | Truth is just a name for verification-processes [James] |
| Full Idea: Truth for us is simply a collective name for verification-processes, just as 'health' is a name for other processes in life. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 6) | |
| A reaction: So the slogan is 'truth is success in belief'? Suicide and racist genocide can be 'successful'. I would have thought that truth was the end of a process, rather than the process itself. |
| 18983 | In many cases there is no obvious way in which ideas can agree with their object [James] |
| Full Idea: When you speak of the 'time-keeping function' of a clock, it is hard to see exactly what your ideas can copy. ...Where our ideas cannot copy definitely their object, what does agreement with that object mean? | |
| From: William James (Pragmatism - eight lectures [1907], Lec 6) | |
| A reaction: This is a very good criticism of the correspondence theory of truth. It looks a lovely theory when you can map components of a sentence (like 'the pen is in the drawer') onto components of reality - but it has to cover the hard cases. |
| 18972 | Ideas are true in so far as they co-ordinate our experiences [James] |
| Full Idea: Pragmatists say that ideas (which themselves are but parts of our experience) become true just in so far as they help us to get into satisfactory relation with other parts of our experience. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 2) | |
| A reaction: I'm struck by the close similarity (at least in James) of the pragmatic view of truth and the coherence theory of truth (associated later with Blanshard). Perhaps the coherence theory is one version of the pragmatic account |
| 18973 | New opinions count as 'true' if they are assimilated to an individual's current beliefs [James] |
| Full Idea: A new opinion counts as 'true' just in proportion as it gratifies the individual's desire to assimilate the novel in his experience to his beliefs in stock. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 2) | |
| A reaction: Note the tell-tale locution 'counts as' true, rather than 'is' true. The obvious problem is that someone with a big stock of foolish beliefs will 'count as' true some bad interpretation which is gratifyingly assimilated to their current confusions. |
| 18984 | True ideas are those we can assimilate, validate, corroborate and verify (and false otherwise) [James] |
| Full Idea: True ideas are those that we can assimilate, validate, corroborate and verify. False ideas are those that we cannot. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 6) | |
| A reaction: The immediate question is why you should label something as 'false' simply on the grounds that you can't corroborate it. Proving the falsity is a stronger position than the ignorance James seems happy with. 'Assimilate' implies coherence. |
| 22305 | If the hypothesis of God is widely successful, it is true [James] |
| Full Idea: On pragmatistic principles, if the hypothesis of God works satisfactorily in the widest sense of the word, it is true. | |
| From: William James (The Meaning of the Word "Truth" [1907], p.299), quoted by Michael Potter - The Rise of Analytic Philosophy 1879-1930 35 'Prag' | |
| A reaction: How you get from 'widely satisfactory' to 'true' is beyond my comprehension. This is dangerous nonsense. This view of truth seems to be a commonplace in American culture. Peirce hurray! James boo! James accepted verification, where possible. |
| 9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
| Full Idea: Two propositions are 'contradictory' if they are never both true and never both false either, which means that ¬(A↔B) is a tautology. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
| Full Idea: We write 'if P then Q' as P→Q. This is called a 'conditional', with P as its 'antecedent', and Q as its 'consequent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: P→Q can also be written as ¬P∨Q. |
| 9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
| Full Idea: If P and Q are any two propositions, the proposition that either P or Q is called the 'disjunction' of P and Q, and is written P∨Q. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.3) | |
| A reaction: This is inclusive-or (meaning 'P, or Q, or both'), and not exlusive-or (Boolean XOR), which means 'P, or Q, but not both'. The ∨ sign is sometimes called 'vel' (Latin). |
| 9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [Lemmon] |
| Full Idea: If P and Q are any two propositions, the proposition that both P and Q is called the 'conjunction' of P and Q, and is written P∧Q. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.3) | |
| A reaction: [I use the more fashionable inverted-v '∧', rather than Lemmon's '&', which no longer seems to be used] P∧Q can also be defined as ¬(¬P∨¬Q) |
| 9508 | The sign |- may be read as 'therefore' [Lemmon] |
| Full Idea: I introduce the sign |- to mean 'we may validly conclude'. To call it the 'assertion sign' is misleading. It may conveniently be read as 'therefore'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: [Actually no gap between the vertical and horizontal strokes of the sign] As well as meaning 'assertion', it may also mean 'it is a theorem that' (with no proof shown). |
| 9512 | We write the 'negation' of P (not-P) as ¬ [Lemmon] |
| Full Idea: We write 'not-P' as ¬P. This is called the 'negation' of P. The 'double negation' of P (not not-P) would be written as ¬¬P. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: Lemmons use of -P is no longer in use for 'not'. A tilde sign (squiggle) is also used for 'not', but some interpreters give that a subtly different meaning (involving vagueness). The sign ¬ is sometimes called 'hook' or 'corner'. |
| 9513 | We write 'P if and only if Q' as P↔Q; it is also P iff Q, or (P→Q)∧(Q→P) [Lemmon] |
| Full Idea: We write 'P if and only if Q' as P↔Q. It is called the 'biconditional', often abbreviate in writing as 'iff'. It also says that P is both sufficient and necessary for Q, and may be written out in full as (P→Q)∧(Q→P). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.4) | |
| A reaction: If this symbol is found in a sequence, the first move in a proof is to expand it to the full version. |
| 9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
| Full Idea: If we say that A and B are 'interderivable' from one another (that is, A |- B and B |- A), then we may write A -||- B. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
| Full Idea: A 'well-formed formula' of the propositional calculus is a sequence of symbols which follows the rules for variables, ¬, →, ∧, ∨, and ↔. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.1) |
| 9528 | A wff is a 'tautology' if all assignments to variables result in the value T [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes the value T for all possible assignments of truth-values to its variables, it is said to be a 'tautology'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [Lemmon] |
| Full Idea: A 'theorem' of logic is the conclusion of a provable sequent in which the number of assumptions is zero. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: This is what Quine and others call a 'logical truth'. |
| 9519 | A 'substitution-instance' is a wff formed by consistent replacing variables with wffs [Lemmon] |
| Full Idea: A 'substitution-instance' is a wff which results by replacing one or more variables throughout with the same wffs (the same wff replacing each variable). | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9529 | A wff is 'inconsistent' if all assignments to variables result in the value F [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes the value F for all possible assignments of truth-values to its variables, it is said to be 'inconsistent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9531 | 'Contrary' propositions are never both true, so that ¬(A∧B) is a tautology [Lemmon] |
| Full Idea: If A and B are expressible in propositional calculus notation, they are 'contrary' if they are never both true, which may be tested by the truth-table for ¬(A∧B), which is a tautology if they are contrary. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9534 | Two propositions are 'equivalent' if they mirror one another's truth-value [Lemmon] |
| Full Idea: Two propositions are 'equivalent' if whenever A is true B is true, and whenever B is true A is true, in which case A↔B is a tautology. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9530 | A wff is 'contingent' if produces at least one T and at least one F [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes at least one T and at least one F for all the assignments of truth-values to its variables, it is said to be 'contingent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9532 | 'Subcontrary' propositions are never both false, so that A∨B is a tautology [Lemmon] |
| Full Idea: If A and B are expressible in propositional calculus notation, they are 'subcontrary' if they are never both false, which may be tested by the truth-table for A∨B, which is a tautology if they are subcontrary. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [Lemmon] |
| Full Idea: The 'scope' of a connective in a certain formula is the formulae linked by the connective, together with the connective itself and the (theoretically) encircling brackets | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.1) |
| 9533 | A 'implies' B if B is true whenever A is true (so that A→B is tautologous) [Lemmon] |
| Full Idea: One proposition A 'implies' a proposition B if whenever A is true B is true (but not necessarily conversely), which is only the case if A→B is tautologous. Hence B 'is implied' by A. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
| Full Idea: Double Negation (DN): Given A, we may derive ¬¬A as a conclusion, and vice versa. The conclusion depends on the assumptions of the premiss. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9393 | A: we may assume any proposition at any stage [Lemmon] |
| Full Idea: Assumptions (A): any proposition may be introduced at any stage of a proof. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9399 | ∧E: Given A∧B, we may derive either A or B separately [Lemmon] |
| Full Idea: And-Elimination (∧E): Given A∧B, we may derive either A or B separately. The conclusions will depend on the assumptions of the premiss. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9398 | ∧I: Given A and B, we may derive A∧B [Lemmon] |
| Full Idea: And-Introduction (&I): Given A and B, we may derive A∧B as conclusion. This depends on their previous assumptions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9397 | CP: Given a proof of B from A as assumption, we may derive A→B [Lemmon] |
| Full Idea: Conditional Proof (CP): Given a proof of B from A as assumption, we may derive A→B as conclusion, on the remaining assumptions (if any). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
| Full Idea: Modus Ponendo Ponens (MPP): Given A and A→B, we may derive B as a conclusion. B will rest on any assumptions that have been made. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
| Full Idea: Or-Elimination (∨E): Given A∨B, we may derive C if it is proved from A as assumption and from B as assumption. This will also depend on prior assumptions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9402 | RAA: If assuming A will prove B∧¬B, then derive ¬A [Lemmon] |
| Full Idea: Reduction ad Absurdum (RAA): Given a proof of B∧¬B from A as assumption, we may derive ¬A as conclusion, depending on the remaining assumptions (if any). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9395 | MTT: Given ¬B and A→B, we derive ¬A [Lemmon] |
| Full Idea: Modus Tollendo Tollens (MTT): Given ¬B and A→B, we derive ¬A as a conclusion. ¬A depends on any assumptions that have been made | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
| Full Idea: Or-Introduction (∨I): Given either A or B separately, we may derive A∨B as conclusion. This depends on the assumption of the premisses. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9521 | 'Modus tollendo ponens' (MTP) says ¬P, P ∨ Q |- Q [Lemmon] |
| Full Idea: 'Modus tollendo ponens' (MTP) says that if a disjunction holds and also the negation of one of its disjuncts, then the other disjunct holds. Thus ¬P, P ∨ Q |- Q may be introduced as a theorem. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: Unlike Modus Ponens and Modus Tollens, this is a derived rule. |
| 9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
| Full Idea: 'Modus ponendo tollens' (MPT) says that if the negation of a conjunction holds and also one of its conjuncts, then the negation of the other conjunct holds. Thus P, ¬(P ∧ Q) |- ¬Q may be introduced as a theorem. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: Unlike Modus Ponens and Modus Tollens, this is a derived rule. |
| 9525 | We can change conditionals into negated conjunctions with P→Q -||- ¬(P ∧ ¬Q) [Lemmon] |
| Full Idea: The proof that P→Q -||- ¬(P ∧ ¬Q) is useful for enabling us to change conditionals into negated conjunctions | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9524 | We can change conditionals into disjunctions with P→Q -||- ¬P ∨ Q [Lemmon] |
| Full Idea: The proof that P→Q -||- ¬P ∨ Q is useful for enabling us to change conditionals into disjunctions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9523 | De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions [Lemmon] |
| Full Idea: The forms of De Morgan's Laws [P∨Q -||- ¬(¬P ∧ ¬Q); ¬(P∨Q) -||- ¬P ∧ ¬Q; ¬(P∧Q) -||- ¬P ∨ ¬Q); P∧Q -||- ¬(¬P∨¬Q)] transform negated conjunctions and disjunctions into non-negated disjunctions and conjunctions respectively. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9527 | The Distributive Laws can rearrange a pair of conjunctions or disjunctions [Lemmon] |
| Full Idea: The Distributive Laws say that P ∧ (Q∨R) -||- (P∧Q) ∨ (P∧R), and that P ∨ (Q∨R) -||- (P∨Q) ∧ (P∨R) | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9526 | We can change conjunctions into negated conditionals with P→Q -||- ¬(P → ¬Q) [Lemmon] |
| Full Idea: The proof that P∧Q -||- ¬(P → ¬Q) is useful for enabling us to change conjunctions into negated conditionals. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9537 | Truth-tables are good for showing invalidity [Lemmon] |
| Full Idea: The truth-table approach enables us to show the invalidity of argument-patterns, as well as their validity. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.4) |
| 9538 | A truth-table test is entirely mechanical, but this won't work for more complex logic [Lemmon] |
| Full Idea: A truth-table test is entirely mechanical, ..and in propositional logic we can even generate proofs mechanically for tautological sequences, ..but this mechanical approach breaks down with predicate calculus, and proof-discovery is an imaginative process. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.5) |
| 9536 | If any of the nine rules of propositional logic are applied to tautologies, the result is a tautology [Lemmon] |
| Full Idea: If any application of the nine derivation rules of propositional logic is made on tautologous sequents, we have demonstrated that the result is always a tautologous sequent. Thus the system is consistent. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.4) | |
| A reaction: The term 'sound' tends to be used now, rather than 'consistent'. See Lemmon for the proofs of each of the nine rules. |
| 9539 | Propositional logic is complete, since all of its tautologous sequents are derivable [Lemmon] |
| Full Idea: A logical system is complete is all expressions of a specified kind are derivable in it. If we specify tautologous sequent-expressions, then propositional logic is complete, because we can show that all tautologous sequents are derivable. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.5) | |
| A reaction: [See Lemmon 2.5 for details of the proofs] |
| 13909 | Write '(∀x)(...)' to mean 'take any x: then...', and '(∃x)(...)' to mean 'there is an x such that....' [Lemmon] |
| Full Idea: Just as '(∀x)(...)' is to mean 'take any x: then....', so we write '(∃x)(...)' to mean 'there is an x such that....' | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) | |
| A reaction: [Actually Lemmon gives the universal quantifier symbol as '(x)', but the inverted A ('∀') seems to have replaced it these days] |
| 13902 | 'Gm' says m has property G, and 'Pmn' says m has relation P to n [Lemmon] |
| Full Idea: A predicate letter followed by one name expresses a property ('Gm'), and a predicate-letter followed by two names expresses a relation ('Pmn'). We could write 'Pmno' for a complex relation like betweenness. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) |
| 13911 | The 'symbols' are bracket, connective, term, variable, predicate letter, reverse-E [Lemmon] |
| Full Idea: I define a 'symbol' (of the predicate calculus) as either a bracket or a logical connective or a term or an individual variable or a predicate-letter or reverse-E (∃). | |
| From: E.J. Lemmon (Beginning Logic [1965], 4.1) |
| 13910 | Our notation uses 'predicate-letters' (for 'properties'), 'variables', 'proper names', 'connectives' and 'quantifiers' [Lemmon] |
| Full Idea: Quantifier-notation might be thus: first, render into sentences about 'properties', and use 'predicate-letters' for them; second, introduce 'variables'; third, introduce propositional logic 'connectives' and 'quantifiers'. Plus letters for 'proper names'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) |
| 13904 | Universal Elimination (UE) lets us infer that an object has F, from all things having F [Lemmon] |
| Full Idea: Our rule of universal quantifier elimination (UE) lets us infer that any particular object has F from the premiss that all things have F. It is a natural extension of &E (and-elimination), as universal propositions generally affirm a complex conjunction. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13906 | With finite named objects, we can generalise with &-Intro, but otherwise we need ∀-Intro [Lemmon] |
| Full Idea: If there are just three objects and each has F, then by an extension of &I we are sure everything has F. This is of no avail, however, if our universe is infinitely large or if not all objects have names. We need a new device, Universal Introduction, UI. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13908 | UE all-to-one; UI one-to-all; EI arbitrary-to-one; EE proof-to-one [Lemmon] |
| Full Idea: Univ Elim UE - if everything is F, then something is F; Univ Intro UI - if an arbitrary thing is F, everything is F; Exist Intro EI - if an arbitrary thing is F, something is F; Exist Elim EE - if a proof needed an object, there is one. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.3) | |
| A reaction: [My summary of Lemmon's four main rules for predicate calculus] This is the natural deduction approach, of trying to present the logic entirely in terms of introduction and elimination rules. See Bostock on that. |
| 13901 | Predicate logic uses propositional connectives and variables, plus new introduction and elimination rules [Lemmon] |
| Full Idea: In predicate calculus we take over the propositional connectives and propositional variables - but we need additional rules for handling quantifiers: four rules, an introduction and elimination rule for the universal and existential quantifiers. | |
| From: E.J. Lemmon (Beginning Logic [1965]) | |
| A reaction: This is Lemmon's natural deduction approach (invented by Gentzen), which is largely built on introduction and elimination rules. |
| 13903 | Universal elimination if you start with the universal, introduction if you want to end with it [Lemmon] |
| Full Idea: The elimination rule for the universal quantifier concerns the use of a universal proposition as a premiss to establish some conclusion, whilst the introduction rule concerns what is required by way of a premiss for a universal proposition as conclusion. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) | |
| A reaction: So if you start with the universal, you need to eliminate it, and if you start without it you need to introduce it. |
| 13905 | If there is a finite domain and all objects have names, complex conjunctions can replace universal quantifiers [Lemmon] |
| Full Idea: If all objects in a given universe had names which we knew and there were only finitely many of them, then we could always replace a universal proposition about that universe by a complex conjunction. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13900 | 'Some Frenchmen are generous' is rendered by (∃x)(Fx→Gx), and not with the conditional → [Lemmon] |
| Full Idea: It is a common mistake to render 'some Frenchmen are generous' by (∃x)(Fx→Gx) rather than the correct (∃x)(Fx&Gx). 'All Frenchmen are generous' is properly rendered by a conditional, and true if there are no Frenchmen. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) | |
| A reaction: The existential quantifier implies the existence of an x, but the universal quantifier does not. |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| Full Idea: The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q. That is, since Napoleon was French, then if the moon is blue then Napoleon was French; and since Napoleon was not Chinese, then if Napoleon was Chinese, the moon is blue. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: This is why the symbol → does not really mean the 'if...then' of ordinary English. Russell named it 'material implication' to show that it was a distinctively logical operator. |
| 13007 | Archimedes defined a straight line as the shortest distance between two points [Archimedes, by Leibniz] |
| Full Idea: Archimedes gave a sort of definition of 'straight line' when he said it is the shortest line between two points. | |
| From: report of Archimedes (fragments/reports [c.240 BCE]) by Gottfried Leibniz - New Essays on Human Understanding 4.13 | |
| A reaction: Commentators observe that this reduces the purity of the original Euclidean axioms, because it involves distance and measurement, which are absent from the purest geometry. |
| 22641 | Realities just are, and beliefs are true of them [James] |
| Full Idea: Realities are not true, they are; and beliefs are true of them. | |
| From: William James (The Pragmatist Account of Truth [1908], 'Fourth') | |
| A reaction: At last, a remark by James about truth which I really like. For 'realities' I would use the word 'facts'. |
| 22649 | Classification can only ever be for a particular purpose [James] |
| Full Idea: Every way of classifying a thing is but a way of handling it for some particular purpose. Conceptions, 'kinds', are teleological instruments. | |
| From: William James (The Sentiment of Rationality [1882], p.24) | |
| A reaction: Could there not be ways of classifying which suit all of our purposes? If there were a naturally correct way to classifying things, then any pragmatist would probably welcome that. (I don't say there is such a way). |
| 18987 | A 'thing' is simply carved out of reality for human purposes [James] |
| Full Idea: What shall we call a 'thing' anyhow? It seems quite arbitrary, for we carve out everything, just as we carve out constellations, to suit our human purposes. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 7) | |
| A reaction: James wrote just before the discovery of galaxies, which are much more obviously 'things' than constellations like the Plough are! This idea suggests a connection between pragmatism and the nihilist view of objects of Van Inwagen and co. |
| 18981 | 'Substance' is just a word for groupings and structures in experience [James] |
| Full Idea: 'Substance' appears now only as another name for the fact that phenomena as they come are actually grouped and given in coherent forms. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 4) | |
| A reaction: This is the strongly empirical strain in James's empiricism. This sounds like a David Lewis comment on the Humean mosaic of experience. We Aristotelians at least believe that the groups run much deeper than the surface of experience. |
| 18974 | Truth is a species of good, being whatever proves itself good in the way of belief [James] |
| Full Idea: Truth is one species of good, and not, as is usually supposed, a category distinct from good, and co-ordinate with it. The true is whatever proves itself to be good in the way of belief, and good, too, for definite, assignable reasons. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 2) | |
| A reaction: The trouble is that false optimism can often often be what is 'good in the way of belief'. That said, I think quite a good way to specify 'truth' is 'success in belief', but I mean intrinsically successful, not pragmatically successful. |
| 18989 | Pragmatism accepts any hypothesis which has useful consequences [James] |
| Full Idea: On pragmatic principles we cannot reject any hypothesis if consequences useful to life flow from it. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 8) | |
| A reaction: Most governments seem to find lies more useful than the truth. Maybe most children are better off not knowing the truth about their parents. It might be disastrous to know the truth about what other people are thinking. Is 'useful but false' meaningful? |
| 22640 | We find satisfaction in consistency of all of our beliefs, perceptions and mental connections [James] |
| Full Idea: We find satisfaction in consistency between the present idea and the entire rest of our mental equipment, including the whole order of our sensations, and that of our intuitions of likeness and difference, and our whole stock previously acquired truths. | |
| From: William James (The Pragmatist Account of Truth [1908], 'Fourth') | |
| A reaction: I like this, apart from the idea that the criterion of good coherence seems to be subjective 'satisfaction'. We should ask why some large set of beliefs is coherent. I assume nature is coherent, and truth is the best explanation of our coherence about it. |
| 22655 | Scientific genius extracts more than other people from the same evidence [James] |
| Full Idea: What is the use of being a genius, unless with the same scientific evidence as other men, one can reach more truth than they? | |
| From: William James (The Sentiment of Rationality [1882], p.40) | |
| A reaction: This is aimed at Clifford's famous principle. He isn't actually contraverting the principle, but it is a nice point about evidence. Simple empiricists think detectives only have to stare at the evidence and the solution creates itself. |
| 22658 | Experimenters assume the theory is true, and stick to it as long as result don't disappoint [James] |
| Full Idea: Each tester of the truth of a theory …acts as if it were true, and expects the result to disappoint him if his assumption is false. The longer disappointment is delayed, the stronger grows his faith in his theory. | |
| From: William James (The Sentiment of Rationality [1882], p.42) | |
| A reaction: This is almost exactly Popper's falsificationist proposal for science, which interestingly shows the close relationship of his view to pragmatism. Believe it as long as it is still working. |
| 18971 | Theories are practical tools for progress, not answers to enigmas [James] |
| Full Idea: Theories are instruments, not answers to enigmas, in which we can rest. We don't lie back upon them, we move forward, and, on occasion, make nature over again by their aid. Pragmatism unstiffens all our theories, limbers them up and sets each one to work. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 2) | |
| A reaction: This follows his criticism of the quest for 'solving names' - big words that give bogus solutions to problems. James's view is not the same as 'instrumentalism', though he would probably sympathise with that view. The defines theories badly. |
| 18985 | True thoughts are just valuable instruments of action [James] |
| Full Idea: The possession of true thoughts means everywhere the possession of invaluable instruments of action. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 6) | |
| A reaction: It looks to me like we should distinguish 'active' and 'passive' instrumentalism. The passive version says there is no more to theories and truth than what instruments record. James's active version says truth is an instrument for doing things well. |
| 18982 | Pragmatism says all theories are instrumental - that is, mental modes of adaptation to reality [James] |
| Full Idea: The pragmatist view is that all our theories are instrumental, are mental modes of adaptation to reality, rather than revelations or gnostic answers to some divinely instituted world enigma. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 5) | |
| A reaction: This treats instrumentalism as the pragmatic idea of theories as what works (and nothing more), with, presumably, no interest in grasping something called 'reality'. Presumably instrumentalism might have other motivations - such as fun. |
| 22654 | We can't know if the laws of nature are stable, but we must postulate it or assume it [James] |
| Full Idea: That nature will follow tomorrow the same laws that she follows today is a truth which no man can know; but in the interests of cognition as well as of action we must postulate or assume it. | |
| From: William James (The Sentiment of Rationality [1882], p.39) | |
| A reaction: The stability of nature is something to be assessed, not something taken for granted. If you arrive in a new city and it all seems quiet, you keep your fingers crossed and treat it as stable. But revolution or coup could be just round the corner. |
| 22656 | Trying to assess probabilities by mere calculation is absurd and impossible [James] |
| Full Idea: The absurd abstraction of an intellect verbally formulating all its evidence and carefully estimating the probability thereof solely by the size of a vulgar fraction, is as ideally inept as it is practically impossible. | |
| From: William James (The Sentiment of Rationality [1882], p.40) | |
| A reaction: James probably didn't know about Bayes, but this is directed at the Bayesian approach. My view is that full rational assessment of coherence is a much better bet than a Bayesian calculation. Factors must be weighted. |
| 22646 | We have a passion for knowing the parts of something, rather than the whole [James] |
| Full Idea: Alongside the passion for simplification …is the passion for distinguishing; it is the passion to be acquainted with the parts rather than to comprehend the whole. | |
| From: William James (The Sentiment of Rationality [1882], p.22) | |
| A reaction: As I child I dismantled almost every toy I was given. This seems to be the motivation for a lot of analytic philosophy, but Aristotle also tended to think that way. |
| 22652 | The mind has evolved entirely for practical interests, seen in our reflex actions [James] |
| Full Idea: It is far too little recognised how entirely the intellect is built up of practical interests. The theory of evolution is beginning to do very good service by its reduction of all mentality to the type of reflex action. | |
| From: William James (The Sentiment of Rationality [1882], p.34) | |
| A reaction: Hands evolved for manipulating tools end up playing the piano. Minds evolved for action can be afflicted with boredom. He's not wrong, but he is risking the etymological fallacy (origin = purpose). I take navigation to be the original purpose of mind. |
| 22651 | Dogs' curiosity only concerns what will happen next [James] |
| Full Idea: A dog's curiosity about the movements of his master or a strange object only extends as far as the point of what is going to happen next. | |
| From: William James (The Sentiment of Rationality [1882], p.31) | |
| A reaction: Good. A nice corrective to people like myself who are tempted to inflate animal rationality, in order to emphasise human evolutionary continuity with them. It is hard to disagree with his observation. But dogs do make judgements! True/false! |
| 9286 | Consciousness is not a stuff, but is explained by the relations between experiences [James] |
| Full Idea: Consciousness connotes a kind of external relation, and not a special stuff or way of being. The peculiarity of our experiences, that they not only are, but are known, is best explained by their relations to one another, the relations being experiences. | |
| From: William James (Does Consciousness Exist? [1904], §3) | |
| A reaction: This view has suddenly caught people's interest. It might be better than the higher/lower relationship, which seems to leave the basic problem untouched. Does a whole network of relations between experiences gradually 'add up' to consciousness? |
| 9285 | 'Consciousness' is a nonentity, a mere echo of the disappearing 'soul' [James] |
| Full Idea: 'Consciousness' is the name of a nonentity. ..Those who cling to it are clinging to a mere echo, the faint rumour left behind by the disappearing 'soul' upon the air of philosophy. ..I deny that it stands for an entity, but it does stand for a function. | |
| From: William James (Does Consciousness Exist? [1904], Intro) | |
| A reaction: This kind of view is often treated as being preposterous, but I think it is correct. No one is denying the phenomenology, but it is the ontology which is at stake. Either you are a substance dualist, or mind must be eliminated as an 'entity'. |
| 23981 | Rage is inconceivable without bodily responses; so there are no disembodied emotions [James] |
| Full Idea: Can one fancy a state of rage and picture no flushing of the face, no dilation of the nostrils, no clenching of the teeth, no impulse to vigorous action? …A purely disembodied human emotion is a nonentity. | |
| From: William James (What is an Emotion? [1884], p.194), quoted by Peter Goldie - The Emotions 3 'Bodily' | |
| A reaction: Plausible for rage, but less so for irritation or admiration. Goldie thinks James is wrong. James says if intellectual feelings don't become bodily then they don't qualify as emotions. No True Scotsman! |
| 22650 | How can the ground of rationality be itself rational? [James] |
| Full Idea: Can that which is the ground of rationality in all else be itself properly called rational? | |
| From: William James (The Sentiment of Rationality [1882], p.25) | |
| A reaction: This is the perennial problem in deciding grounds, and in deciding what to treat as primitive. The stoics see the whole of nature as rational. Cf how can the ground of what is physical be itself physical? |
| 22643 | It seems that we feel rational when we detect no irrationality [James] |
| Full Idea: I think there are very good grounds for upholding the view that the feeling of rationality is constituted merely by the absence of any feelings of irrationality. | |
| From: William James (The Sentiment of Rationality [1882], p.20) | |
| A reaction: A very interesting proposal. Nothing is more basic to logic (well, plausible versions of logic) than the principle of non-contradiction - perhaps because it is the foundation of our natural intellectual equipment. |
| 18975 | We return to experience with concepts, where they show us differences [James] |
| Full Idea: Concepts for the pragmatist are things to come back into experience with, things to make us look for differences. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 3) | |
| A reaction: That's good. I like both halves of this. Experience gives us the concepts, but then we 'come back' into experience equipped with them. Presumably animals can look for differences, but concepts enhance that hugely. Know the names of the flowers. |
| 22660 | Evolution suggests prevailing or survival as a new criterion of right and wrong [James] |
| Full Idea: The philosophy of evolution offers us today a new criterion, which is objective and fixed, as an ethical test between right and wrong: That is to be called good which is destined to prevail or survive. | |
| From: William James (The Sentiment of Rationality [1882], p.44) | |
| A reaction: Perceptive for its time. Herbert Spencer may have suggested the idea. James dismisses it, because it implies a sort of fatalism, whereas genuine moral choices are involved in what survives. |
| 6570 | Imagine millions made happy on condition that one person suffers endless lonely torture [James] |
| Full Idea: Consider a case in which millions could be made permanently happy on the one simple condition that a certain lost soul on the far-off edge of things should lead a life of lonely torture. | |
| From: William James (The Will to Believe [1896], p.188), quoted by Robert Fogelin - Walking the Tightrope of Reason Ch.2 | |
| A reaction: This seems to be one of the earliest pinpointings of a key problem with utilitiarianism, which is that other values than happiness (in this case, fairness) seem to be utterly overruled. If we ignore fairness, why shouldn't we ignore happiness? |
| 22645 | Understanding by means of causes is useless if they are not reduced to a minimum number [James] |
| Full Idea: The knowledge of things by their causes, which is often given as a definition of rational knowledge, is useless unless the causes converge to a minimum number, while still producing the maximum number of effects. | |
| From: William James (The Sentiment of Rationality [1882], p.21) | |
| A reaction: This is certainly the psychological motivation for trying to identify 'the' cause of something, but James always tries to sell such things as subjective. 'Useless' to one person is a subjective criterion; useless to anyone is much more objective. |
| 18980 | If there is a 'greatest knower', it doesn't follow that they know absolutely everything [James] |
| Full Idea: The greatest knower of them all may yet not know the whole of everything, or even know what he does know at one single stroke: - he may be liable to forget. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 4) | |
| A reaction: And that's before you get to the problem of how the greatest knower could possibly know whether or not they knew absolutely everything, or whether there might be some fact which was irremediably hidden from them. |
| 18978 | It is hard to grasp a cosmic mind which produces such a mixture of goods and evils [James] |
| Full Idea: We can with difficulty comprehend the character of a cosmic mind whose purposes are fully revealed by the strange mixture of good and evils that we find in this actual world's particulars. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 3) | |
| A reaction: And, of course, what counts as 'goods' or 'evils' seems to have a highly relative aspect to it. To claim that really it is all good is massive hope based on flimsy evidence. |
| 18991 | If the God hypothesis works well, then it is true [James] |
| Full Idea: On pragmatistic principles, if the hypothesis of God works satisfactorily in the widest sense of the word, it is true. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 8) | |
| A reaction: The truth of God's existence certainly is a challenging test case for the pragmatic theory of truth, and James really bites the bullet here. Pragmatism may ultimately founder on the impossibility of specifying what 'works satisfactorily' means. |
| 18977 | The wonderful design of a woodpecker looks diabolical to its victims [James] |
| Full Idea: To the grub under the bark the exquisite fitness of the woodpecker's organism to extract him would certainly argue a diabolical designer. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 3) | |
| A reaction: What an elegant sentence! The huge problem for religious people who accept (probably reluctantly) evolution by natural selection is the moral nature of the divine being who could use such a ruthless method of design. |
| 18979 | Things with parts always have some structure, so they always appear to be designed [James] |
| Full Idea: The parts of things must always make some definite resultant, be it chaotic or harmonious. When we look at what has actually come, the conditions must always appear perfectly designed to ensure it. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 3) | |
| A reaction: In so far as the design argument is an analogy with human affairs, we can't deny that high levels of order suggest an organising mind, and mere chaos suggests a coincidence of unco-ordinated forces. |
| 18976 | Private experience is the main evidence for God [James] |
| Full Idea: I myself believe that the evidence for God lies primarily in inner personal experience. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 3) | |
| A reaction: There is not much you can say to someone who claims incontrovertible evidence which is utterly private to themselves. Does total absence of private religious experience count as evidence on the subject? |
| 22653 | Early Christianity says God recognises the neglected weak and tender impulses [James] |
| Full Idea: In what did the emancipating message of primitive Christianity consist but in the announcement that God recognizes those weak and tender impulses which paganism had so rudely overlooked. | |
| From: William James (The Sentiment of Rationality [1882], p.36) | |
| A reaction: Nietzsche says these are the virtues of a good slave. Previous virtues were dominated by military needs, but the new virtues are those of large cities, where communal living with strangers is the challenge. |
| 18990 | Nirvana means safety from sense experience, and hindus and buddhists are just afraid of life [James] |
| Full Idea: Nirvana means safety from the everlasting round of adventures of which the world of sense consists. The hindoo and the buddhist for this is essentially their attitude, are simply afraid, afraid of more experience, afraid of life. | |
| From: William James (Pragmatism - eight lectures [1907], Lec 8) | |
| A reaction: Wonderfully American! From what I have seen of eastern thought, including Taoism, I agree with James, in general. There is a rejection of knowledge and of human life which I find shocking. I suspect it is a defence mechanism for downtrodden people. |