35 ideas
11051 | Frege's logical approach dominates the analytical tradition [Hanna] |
Full Idea: Pure logic constantly controls Frege's philosophy, and in turn Frege's logically oriented philosophy constantly controls the analytic tradition. | |
From: Robert Hanna (Rationality and Logic [2006], 1.1) | |
A reaction: Hanna seeks to reintroduce the dreaded psychological aspect of logic, and I say 'good for him'. |
11054 | Scientism says most knowledge comes from the exact sciences [Hanna] |
Full Idea: Scientism says that the exact sciences are the leading sources of knowledge about the world. | |
From: Robert Hanna (Rationality and Logic [2006], 1.2) | |
A reaction: I almost agree, but I would describe the exact sciences as the chief 'evidence' for our knowledge, with the chief 'source' being our own ability to make coherent sense of the evidence. Exact sciences rest on mathematics. |
11070 | 'Denying the antecedent' fallacy: φ→ψ, ¬φ, so ¬ψ [Hanna] |
Full Idea: The fallacy of 'denying the antecedent' is of the form φ→ψ, ¬φ, so ¬ψ. | |
From: Robert Hanna (Rationality and Logic [2006], 5.4) |
11071 | 'Affirming the consequent' fallacy: φ→ψ, ψ, so φ [Hanna] |
Full Idea: The fallacy of 'affirming the consequent' is of the form φ→ψ, ψ, so φ. | |
From: Robert Hanna (Rationality and Logic [2006], 5.4) |
11088 | We can list at least fourteen informal fallacies [Hanna] |
Full Idea: Informal fallacies: appeals to force, circumstantial factors, ignorance, pity, popular consensus, authority, generalisation, confused causes, begging the question, complex questions, irrelevance, equivocation, black-and-white, slippery slope etc. | |
From: Robert Hanna (Rationality and Logic [2006], 7.3) |
11059 | Circular arguments are formally valid, though informally inadmissible [Hanna] |
Full Idea: A circular argument - one whose conclusion is to be found among its premises - is inadmissible in most informal contexts, even though it is formally valid. | |
From: Robert Hanna (Rationality and Logic [2006], 2.1) | |
A reaction: Presumably this is a matter of conversational implicature - that you are under a conventional obligation to say things which go somewhere, rather than circling around their starting place. |
11089 | Formally, composition and division fallacies occur in mereology [Hanna] |
Full Idea: Informal fallacies of composition and division go over into formal fallacies of mereological logic. | |
From: Robert Hanna (Rationality and Logic [2006], 7.3) |
11058 | Logic is explanatorily and ontologically dependent on rational animals [Hanna] |
Full Idea: Logic is explanatorily and ontologically dependent on rational animals. | |
From: Robert Hanna (Rationality and Logic [2006], 1.6) | |
A reaction: This is a splendid defiance of the standard Fregean view of logic as having an inner validity of its own, having nothing to do with the psychology of thinkers. But if Hanna is right, why does logical consequence seem to be necessary? |
11072 | Logic is personal and variable, but it has a universal core [Hanna] |
Full Idea: Beyond an innate and thus universally share protologic, each reasoner's mental logic is only more or less similar to the mental logic of any other reasoner. | |
From: Robert Hanna (Rationality and Logic [2006], 5.7) | |
A reaction: This is the main thesis of Hanna's book. I like the combination of this idea with Stephen Read's remark that each student should work out a personal logic which has their own private endorsement. |
11061 | Intensional consequence is based on the content of the concepts [Hanna] |
Full Idea: In intensional logic the consequence relation is based on the form or content of the concepts or properties expressed by the predicates. | |
From: Robert Hanna (Rationality and Logic [2006], 2.2) |
11063 | Logicism struggles because there is no decent theory of analyticity [Hanna] |
Full Idea: All versions of the thesis that arithmetic is reducible to logic remain questionable as long as no good theory of analyticity is available. | |
From: Robert Hanna (Rationality and Logic [2006], 2.4) | |
A reaction: He rejects the attempts by Frege, Wittgenstein and Carnap to provide a theory of analyticity. |
11055 | Supervenience can add covariation, upward dependence, and nomological connection [Hanna] |
Full Idea: 'Strong supervenience' involves necessary covariation of the properties, and upward dependence of higher level on lower level. ...If we add a nomological connection between the two, then we have 'superdupervenience'. | |
From: Robert Hanna (Rationality and Logic [2006], 1.2) | |
A reaction: [compressed] Very helpful. A superdupervenient relationship between mind and brain would be rather baffling if they were not essentially the same thing. (which is what I take them to be). |
18529 | Relations are expressed either as absolute facts, or by a relational concept [William of Ockham] |
Full Idea: Socrates and Plato are similar if they are both white. Yet the mind can express this either by an 'absolute concept' (as 'Socrates is white' and 'Plato is white'), or by a 'relative concept', as 'Socrates is similar to Plato with respect to whiteness. | |
From: William of Ockham (Seven Quodlibets [1332], VI q.25), quoted by John Heil - The Universe as We Find It 7 | |
A reaction: Presumably he takes the facts of the matter to be the absolute concept, and the relative concept to be a contribution of the intellect. |
16779 | Cut wood doesn't make a new substance, but seems to make separate subjects [William of Ockham] |
Full Idea: When a piece of wood is divided in two halves, no new substance is generated. But there are now two substances, or the accidents of the two halves would be without a subject. They existed before hand, and were one piece of wood, but not in the same place. | |
From: William of Ockham (Seven Quodlibets [1332], IV.19), quoted by Richard S. Westfall - Never at Rest: a biography of Isaac Newton 26.2 | |
A reaction: A nice example, demonstrating that there are substances within substances, contrary to the view of Duns Scotus. If a substance is just a subject for properties, it is hard to know what to make of this case. |
16757 | Hot water naturally cools down, which is due to the substantial form of the water [William of Ockham] |
Full Idea: It is clear to the senses that hot water, if left to its own nature, reverts to coldness; this coldness cannot be caused by anything other than the substantial form of the water. | |
From: William of Ockham (Seven Quodlibets [1332], III.6), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 24.4 | |
A reaction: Unfortunately this is very bad science (even for its time), but it shows how many scholastics treated hylomorphism as a very physical and causal theory. |
11083 | A sentence is necessary if it is true in a set of worlds, and nonfalse in the other worlds [Hanna] |
Full Idea: On my view, necessity is the truth of a sentence in every member of a set of possible worlds, together with its nonfalsity in every other possible worlds. | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) |
11086 | Metaphysical necessity can be 'weak' (same as logical) and 'strong' (based on essences) [Hanna] |
Full Idea: Weak metaphysical necessity is either over the set of all logically possible worlds (in which case it is the same as logical necessity), or it is of a smaller set of worlds, and is determined by the underlying essence or nature of the actual world. | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) | |
A reaction: I take the first to be of no interest, as I have no interest in a world which is somehow rated as logically possible, but is not naturally possible. The second type should the principle aim of all human cognitive enquiry. The strong version is synthetic. |
11084 | Logical necessity is truth in all logically possible worlds, because of laws and concepts [Hanna] |
Full Idea: Logical necessity is the truth of a sentence by virtue of logical laws or intrinsic conceptual connections alone, and thus true in all logically possible worlds. Put in traditional terms, logical necessity is analyticity. | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) |
11085 | Nomological necessity is truth in all logically possible worlds with our laws [Hanna] |
Full Idea: Physical or nomological necessity is the truth of a sentence in all logically possible worlds governed by our actual laws of nature. | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) | |
A reaction: Personally I think 'natural necessity' is the best label for this, as it avoids firm commitment to reductive physicalism, and it also avoids commitment to actual necessitating laws. |
19440 | How do you know you have conceived a thing deeply enough to assess its possibility? [Vaidya] |
Full Idea: The main issue with learning possibility from conceivability concerns how we can be confident that we have conceived things to the relevant level of depth required for the scenario to actually be a presentation or manifestation of a genuine possibility. | |
From: Anand Vaidya (The Epistemology of Modality [2015], 1.2.2) | |
A reaction: [He cites Van Inwagen 1998 for this idea] The point is that ignorant imagination can conceive of all sorts of absurd things which are seen to be impossible when enough information is available. We can hardly demand a criterion for this. |
11077 | Intuition includes apriority, clarity, modality, authority, fallibility and no inferences [Hanna] |
Full Idea: The nine features of intuition are: a mental act, apriority, content-comprehensiveness, clarity and distinctness, strict-modality-attributivity, authoritativeness,noninferentiality, cognitive indispensability, and fallibility. | |
From: Robert Hanna (Rationality and Logic [2006], 6.4) | |
A reaction: [See Hanna for a full explanation of this lot] Seems like a good stab at it. Note the trade-off between authority and fallibility. |
11080 | Intuition is more like memory, imagination or understanding, than like perception [Hanna] |
Full Idea: There is no reason why intuition should be cognitively analogous not to sense perception but instead to either memory, imagination, or conceptual understanding. | |
From: Robert Hanna (Rationality and Logic [2006], 6.5) | |
A reaction: It is Russell's spotting the analogy with memory that made me come to believe that a priori knowledge is possible, as long as we accept it as being fallible. [Hanna has a good discussion of intuition; he votes for the imagination analogy] |
11078 | Intuition is only outside the 'space of reasons' if all reasons are inferential [Hanna] |
Full Idea: Intuition is outside the 'space of reasons' if we assume that all reasons are inferential, but inside if we assume that reasons need not always be inferential. | |
From: Robert Hanna (Rationality and Logic [2006], 6.4) | |
A reaction: I take it that intuition can be firmly inside the space of reasons, and that not all reasons are inferential. |
11053 | Explanatory reduction is stronger than ontological reduction [Hanna] |
Full Idea: As standardly construed, reduction can be either explanatory or ontological. Explanatory reduction is the strongest sort of reduction. ...Ontological reduction can still have an 'explanatory gap'. | |
From: Robert Hanna (Rationality and Logic [2006], 1.1) |
11081 | Imagination grasps abstracta, generates images, and has its own correctness conditions [Hanna] |
Full Idea: Three features of imagination are that its objects can be abstract, that it generates spatial images directly available to introspection, and its correctness conditions are not based on either efficacious causation or effective tracking. | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) | |
A reaction: Hanna makes the imagination faculty central to our grasp of his proto-logic. |
9102 | If an animal approached from a distance, we might abstract 'animal' from one instance [William of Ockham] |
Full Idea: It seems possible that the concept of a genus could be abstracted from one individual, let us say, the concept 'animal', as in the case of one approaching from a distance, when I see enough to judge that I am seeing an animal. | |
From: William of Ockham (Seven Quodlibets [1332], I Q xiii) | |
A reaction: This is a rather individualistic view of abstraction, ignoring the shared language and culture. It is hard to imagine a truly virgin mind coming up with the concept after one encounter. The concept 'mind-boggling' seems more likely. |
9114 | There are no secure foundations to prove the separate existence of mind, in reason or experience [William of Ockham] |
Full Idea: The existence of an immaterial 'intellective soul' ..cannot be demonstrated; for every reason by which we try to prove it assumes something that is doubtful for a man who follows only his natural reason. Neither can it be proved by experience. | |
From: William of Ockham (Seven Quodlibets [1332], I Q x) | |
A reaction: This is splendid honesty from a medieval monk. How would such a clear thinker have responded to modern brain research? Colin McGinn still maintains William's view, despite modern knowledge. Our ignorance produced conceptual dualism. |
11082 | Should we take the 'depictivist' or the 'descriptivist/propositionalist' view of mental imagery? [Hanna] |
Full Idea: In the debate in cognitive science on the nature of mental imagery, there is a 'depictivist' side (Johnson-Laird, Kosslyn, Shepard - good images are isomorphic), and a 'descriptivist' or 'propositionalist' side (Pylyshyn and others). | |
From: Robert Hanna (Rationality and Logic [2006], 6.6) | |
A reaction: Hanna votes firmly in favour of the first view, and implies that they have more or less won the debate. |
11067 | Rational animals have a normative concept of necessity [Hanna] |
Full Idea: A rational animal is one that is a normative-reflective possessor of the concepts of necessity, certainty and unconditional obligation. | |
From: Robert Hanna (Rationality and Logic [2006], 4.0) | |
A reaction: The addition of obligation shows the Kantian roots of this. It isn't enough just to possess a few concepts. You wouldn't count as rational if you didn't desire truth, as well as understanding it. Robots be warned. |
11068 | One tradition says talking is the essence of rationality; the other says the essence is logic [Hanna] |
Full Idea: In the tradition of Descartes, Chomsky and Davidson, rational animals are essentially talking animals. But in the view of Kant, and perhaps Fodor, it is the cognitive capacity for logic that is the essence of human rationality. | |
From: Robert Hanna (Rationality and Logic [2006], 4.9) |
11047 | Hegelian holistic rationality is the capacity to seek coherence [Hanna] |
Full Idea: The 'holistic' (Hegelian) sense of rationality means the capacity for systematically seeking coherence (or 'reflective equilibrium') across a network or web of beliefs, desires, emotions, intentions and volitions. Traditionally 'the truth is the whole'. | |
From: Robert Hanna (Rationality and Logic [2006], Intro) | |
A reaction: On the whole this is my preferred view (which sounds Quinean as well as Hegelian), though I reject the notion that truth is a whole. I take coherence to be the hallmark of justification, though not of truth, and reason aims to justify. |
11048 | Humean Instrumental rationality is the capacity to seek contingent truths [Hanna] |
Full Idea: The 'instrumental' (Humean) sense of rationality means a capacity for generating or recognizing contingent truths, contextually normative rules, consequentialist obligations, and hypothetical 'ought' claims. Reason is 'the slave of the passions'. | |
From: Robert Hanna (Rationality and Logic [2006], Intro) |
11046 | Kantian principled rationality is recognition of a priori universal truths [Hanna] |
Full Idea: The 'principled' (Kantian) sense of rationality means the possession of a capacity for generating or recognizing necessary truths, a priori beliefs, strictly universal normative rules, nonconsequentialist moral obligations, and categorical 'ought' claims. | |
From: Robert Hanna (Rationality and Logic [2006], Intro) |
11045 | Most psychologists are now cognitivists [Hanna] |
Full Idea: Most psychologists have now dropped behaviourism and adopted cognitivism: the thesis that the rational human mind is essentially an active innately specified information-processor. | |
From: Robert Hanna (Rationality and Logic [2006], Intro) |
9115 | To love God means to love whatever God wills to be loved [William of Ockham] |
Full Idea: To love God above all means to love whatever God wills to be loved. | |
From: William of Ockham (Seven Quodlibets [1332], III Q xiii) | |
A reaction: A striking thought, which could be meaningful to the non-religious. Is it possible to form an image of what a perfect and ideal mind would love most? This might generate a set of universal values. It is tricky to find out what an actual God loves. |