78 ideas
| 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) |
| 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) |
| 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) |
| 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) |
| 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'. |
| 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) |
| 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) |
| 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. |
| 14308 | We can bring dispositions into existence, as in creating an identifier [Dennett, by Mumford] |
| Full Idea: We can bring a real disposition into existence, as in Dennett's case of a piece of cardboard torn in half, so that two strangers can infallibly identify one another. | |
| From: report of Daniel C. Dennett (Consciousness Explained [1991], p.376) by Stephen Mumford - Dispositions 03.7 n37 | |
| A reaction: Presumably human artefacts in general qualify as sets of dispositions which we have created. |
| 7384 | Words are fixed by being attached to similarity clusters, without mention of 'essences' [Dennett] |
| Full Idea: We don't need 'essences' or 'criteria' to keep the meaning of our word from sliding all over the place; our words will stay put, quite firmly attached as if by gravity to the nearest similarity cluster. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.2) | |
| A reaction: Plausible, but essentialism (which may have been rejuventated by a modern theory of reference in language) is not about language. It is offering an explanation of why there are 'similarity clusters. Organisms are too complex to have pure essences. |
| 7374 | Light wavelengths entering the eye are only indirectly related to object colours [Dennett] |
| Full Idea: The wavelengths of the light entering the eye are only indirectly related to the colours we see objects to be. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 12.2) | |
| A reaction: This is obviously bad news for naïve realism, but I also take it as good support for the primary/secondary distinction. I just can't make sense of anyone claiming that colour exists anywhere else except in the brain. |
| 7369 | Brains are essentially anticipation machines [Dennett] |
| Full Idea: All brains are, in essence, anticipation machines. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 7.2) | |
| A reaction: This would necessarily, I take it, make them induction machines. So brains will only evolve in a world where induction is possible, which is one where there a lot of immediately apprehensible regularities. |
| 7393 | We can't draw a clear line between conscious and unconscious [Dennett] |
| Full Idea: Even in our own case, we cannot draw the line separating our conscious mental states from our unconscious mental states. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 14.2) | |
| A reaction: This strikes me as being a simple and self-evident truth, which anyone working on the brain takes for granted, but an awful lot of philosophers (stuck somewhere in the seventeenth century) can't seem to grasp. |
| 7367 | Perhaps the brain doesn't 'fill in' gaps in consciousness if no one is looking. [Dennett] |
| Full Idea: Perhaps the brain doesn't actually have to go to the trouble of "filling in" anything with "construction" - for no one is looking. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 5.4) | |
| A reaction: This a very nice point, because claims that the mind fills in in various psychological visual tests always has the presupposition of a person (or homunculus?) which is overseeing the visual experiences. |
| 7394 | Conscious events can only be explained in terms of unconscious events [Dennett] |
| Full Idea: Only a theory that explained conscious events in terms of unconscious events could explain consciousness at all. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 14.4) | |
| A reaction: This sounds undeniable, so it seems to force a choice between reductive physicalism and mysterianism. Personally I think there must be an explanation in terms of non-conscious events, even if humans are too thick to understand it. |
| 7391 | We can know a lot of what it is like to be a bat, and nothing important is unknown [Dennett] |
| Full Idea: There is at least a lot that we can know about what it is like to be a bat, and Nagel has not given us a reason to believe there is anything interesting or theoretically important that is inaccessible to us. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 14.2) | |
| A reaction: I agree. If you really wanted to identify with the phenomenology of bathood, you could spend a lot of time in underground caves whistling with your torch turned off. I can't, of course, be a bat, but then I can't be my self of yesterday. |
| 7387 | "Qualia" can be replaced by complex dispositional brain states [Dennett] |
| Full Idea: "Qualia" can be replaced by complex dispositional states of the brain. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 14.1) | |
| A reaction: 'Dispositional' reveals Dennett's behaviourist roots (he was a pupil of Ryle). Fodor is right that physicalism cannot just hide behind the word "complexity". That said, the combination of complexity and speed might add up to physical 'qualia'. |
| 7376 | We can't assume that dispositions will remain normal when qualia have been inverted [Dennett] |
| Full Idea: The goal of the experiment was to describe a case in which it was obvious that the qualia would be inverted while the reactive dispositions would be normalized. But the assumption that one could just tell is question-begging. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 12.4) | |
| A reaction: It certainly seems simple and plausible that if we inverted our experience of traffic light colours, no difference in driver behaviour would be seen. However, my example, of a conversation in a gallery of abstract art, seems more problematic. |
| 7372 | In peripheral vision we see objects without their details, so blindsight is not that special [Dennett] |
| Full Idea: If a playing card is held in peripheral vision, we can see the card without being able to identify its colours or its shapes. That's normal sight, not blindsight, so we should be reluctant on those grounds to deny visual experience to blindsight subjects. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 11.4) | |
| A reaction: This is an important point in Dennett's war against the traditional all-or-nothing view of mental events. Nevertheless, blindsight subjects deny all mental experience, while picking up information, and peripheral vision never seems like that. |
| 7373 | Blindsight subjects glean very paltry information [Dennett] |
| Full Idea: Discussions of blindsight have tended to ignore just how paltry the information is that blindsight subjects glean from their blind fields. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 11.4) | |
| A reaction: This is a bit unfair, because blindsight has mainly pointed to interesting speculations (e.g. Idea 2953). Nevertheless, if blindsight with very high information content is actually totally impossible, the speculations ought to be curtailed. |
| 7385 | People accept blurred boundaries in many things, but insist self is All or Nothing [Dennett] |
| Full Idea: Many people are comfortable taking the pragmatic approach to night/day, living/nonliving and mammal/premammal, but get anxious about the same attitude to having a self and not having a self. It must be All or Nothing, and One to a Customer. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.2) | |
| A reaction: Personally I think I believe in the existence of the self, but I also agree with Dennett. I greatly admire his campaign against All or Nothing thinking, which is a relic from an earlier age. A partial self could result from infancy or brain damage. |
| 7383 | The psychological self is an abstraction, not a thing in the brain [Dennett] |
| Full Idea: Like the biological self, the psychological or narrative self is an abstraction, not a thing in the brain. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.1) | |
| A reaction: Does Dennett have empirical evidence for this claim? It seems to me perfectly possible that there is a real thing called the 'self', and it is the central controller of the brain (involving propriotreptic awareness, understanding, and will). |
| 7386 | Selves are not soul-pearls, but artefacts of social processes [Dennett] |
| Full Idea: Selves are not independently existing soul-pearls, but artefacts of the social processes that create us, and, like other such artefacts, subject to sudden shifts in status. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.2) | |
| A reaction: "Soul-pearls" is a nice phrase for the Cartesian view, but there can something between soul-pearls and social constructs. Personally I think the self is a development of the propriotreptic (body) awareness that even the smallest animals must possess. |
| 7381 | We tell stories about ourselves, to protect, control and define who we are [Dennett] |
| Full Idea: Our fundamental tactic of self-protection, self-control and self-definition is telling stories, and more particularly concocting and controlling the story we tell others - and ourselves - about who we are. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.1) | |
| A reaction: This seems to suggest that there is someone who wants to protect themselves, and who wants to tell the stories, and does tell the stories. No one can deny the existence of this autobiographical element in our own identity. |
| 7382 | We spin narratives about ourselves, and the audience posits a centre of gravity for them [Dennett] |
| Full Idea: The effect of our string of personal narratives is to encourage the audience to (try to) posit a unified agent whose words they are, about whom they are: in short, to posit a centre of narrative gravity. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 13.1) | |
| A reaction: What would be the evolutionary advantage of getting the audience to posit a non-existent self, instead of a complex brain? It might be simpler than that, since we say of a bird "it wants to do x". What is "it"? Some simple thing, like a will. |
| 7370 | The brain is controlled by shifting coalitions, guided by good purposeful habits [Dennett] |
| Full Idea: Who's in charge of the brain? First one coalition and then another, shifting in ways that are not chaotic thanks to good meta-habits that tend to entrain coherent, purposeful sequences rather than an interminable helter-skelter power grab. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 8.1) | |
| A reaction: This is probably the best anti-ego account available. Dennett offers our sense of self as a fictional autobiography, but the sense of a single real controller is very powerful. If I jump at a noise, I feel that 'I' have lost control of myself. |
| 7379 | If an epiphenomenon has no physical effects, it has to be undetectable [Dennett] |
| Full Idea: Psychologists mean a by-product by an 'epiphenomenon', ...but the philosophical meaning is too strong: it yields a concept of no utility whatsoever. Since x has no physical effects (according to the definition), no instrument can detect it. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 12.5) | |
| A reaction: Well said! This has always been my half-formulated intuition about the claim that the mind (or anything) might be totally epiphenomenal. All a thing such as the reflection on a lake can be is irrelevant to the functioning of that specified system. |
| 7365 | Dualism wallows in mystery, and to accept it is to give up [Dennett] |
| Full Idea: Given the way dualism wallows in mystery, accepting dualism is giving up. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 2.4) | |
| A reaction: Some things, of course, might be inherently mysterious to us, and we might as well give up. The big dualist mystery is the explanation of how such different substances can interact. How do two physical substances manage to interact? |
| 7371 | All functionalism is 'homuncular', of one grain size or another [Dennett] |
| Full Idea: All varieties of functionalism can be viewed as 'homuncular' functionalism of one grain size or another. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 9.2) | |
| A reaction: This seems right, as any huge and complex mechanism (like a moon rocket) will be made up of some main systems, then sub-systems, then sub-sub-sub.... This assumes that there are one or two overarching purposes, which there are in people. |
| 7380 | Visual experience is composed of neural activity, which we find pleasing [Dennett] |
| Full Idea: All visual experience is composed of activities of neural circuits whose very activity is innately pleasing to us. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 12.6) | |
| A reaction: This is the nearest I can find to Dennett saying something eliminativist. It seems to beg the question of who 'us' refers to, and what is being pleased, and how it is 'pleased' by these neural circuits. The Hard Question? |
| 7366 | It is arbitrary to say which moment of brain processing is conscious [Dennett] |
| Full Idea: If one wants to settle on some moment of processing in the brain as the moment of consciousness, this has to be arbitrary. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 5.3) | |
| A reaction: Seems eliminativist, as it implies that all that is really going on is 'processing'. But there are two senses of 'arbitrary' - that calling it consciousness is arbitrary (wrong), or thinking that mind doesn't move abruptly into consciousness (right). |
| 7368 | Originally there were no reasons, purposes or functions; since there were no interests, there were only causes [Dennett] |
| Full Idea: In the beginning there were no reasons; there were only causes. Nothing had a purpose, nothing had so much as a function; there was no teleology in the world at all. The explanation is simple: there was nothing that had interests. | |
| From: Daniel C. Dennett (Consciousness Explained [1991], 7.2) | |
| A reaction: It seems reasonable to talk of functions even if the fledgling 'interests' are unconscious, as in a leaf. Is a process leading to an end an 'interest'? What are the 'interests' of a person who is about to commit suicide? |
| 16713 | Philosophers are the forefathers of heretics [Tertullian] |
| Full Idea: Philosophers are the forefathers of heretics. | |
| From: Tertullian (works [c.200]), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 20.2 |
| 6610 | I believe because it is absurd [Tertullian] |
| Full Idea: I believe because it is absurd ('Credo quia absurdum est'). | |
| From: Tertullian (works [c.200]), quoted by Robert Fogelin - Walking the Tightrope of Reason n4.2 | |
| A reaction: This seems to be a rather desperate remark, in response to what must have been rather good hostile arguments. No one would abandon the support of reason if it was easy to acquire. You can't deny its engaging romantic defiance, though. |