34 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) |
23026 | We know mathematical axioms, such as subtracting equals from equals leaves equals, by a natural light [Leibniz] |
Full Idea: It is by the natural light that the axioms of mathematics are recognised. If we take away the same quantity from two equal things, …a thing we can easily predict without having experienced it. | |
From: Gottfried Leibniz (Letters to Queen Charlotte [1702], p.189) | |
A reaction: He also says two equal weights will keep a balance level. Plato thinks his slave boy understands halving an area by the natural light, but that is just as likely to be experience. It is too easy to attribut thoughts to a 'natural light'. |
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). |
13189 | A necessary feature (such as air for humans) is not therefore part of the essence [Leibniz] |
Full Idea: That which is necessary for something does not constitute its essence. Air is necessary for our life, but our life is something other than air. | |
From: Gottfried Leibniz (Letters to Queen Charlotte [1702], 1702) | |
A reaction: Bravo. Why can't modern philosophers hang on to this distinction? They seem to think that because they don't believe in traditional essences they can purloin the word for something else. Same with the word 'abstraction'. |
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. |
19432 | Intelligible truth is independent of any external things or experiences [Leibniz] |
Full Idea: Intelligible truth is independent of the truth or of the existence outside us of sensible and material things. ....It is generally true that we only know necessary truths by the natural light [of reason] | |
From: Gottfried Leibniz (Letters to Queen Charlotte [1702], 1702) | |
A reaction: A nice quotation summarising a view for which Leibniz is famous - that there is a tight correlation between necessary truths and our a priori knowledge of them. The obvious challenge comes from Kripke's claim that scientists can discover necessities. |
19430 | We know objects by perceptions, but their qualities don't reveal what it is we are perceiving [Leibniz] |
Full Idea: We use the external senses ...to make us know their particular objects ...but they do not make us know what those sensible qualities are ...whether red is small revolving globules causing light, heat a whirling of dust, or sound is waves in air. | |
From: Gottfried Leibniz (Letters to Queen Charlotte [1702], 1702) | |
A reaction: These seems to be exactly the concept of secondary qualities which Locke was promoting. They are unreliable information about the objects we perceive. Primary qualities are reliable information. I like that distinction. |
19431 | There is nothing in the understanding but experiences, plus the understanding itself, and the understander [Leibniz] |
Full Idea: It can be said that there is nothing in the understanding which does not come from the senses, except the understanding itself, or that which understands. | |
From: Gottfried Leibniz (Letters to Queen Charlotte [1702], 1702) | |
A reaction: Given that Leibniz is labelled as a 'rationalist', this is awfully close to empiricism. Not Locke's 'tabula rasa' perhaps, but Hume's experiences plus associations. Leibniz has a much loftier notion of understanding and reason than Hume does. |
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. |
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. |
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) |
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) |
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) |
7903 | The six perfections are giving, morality, patience, vigour, meditation, and wisdom [Nagarjuna] |
Full Idea: The six perfections are of giving, morality, patience, vigour, meditation, and wisdom. | |
From: Nagarjuna (Mahaprajnaparamitashastra [c.120], 88) | |
A reaction: What is 'morality', if giving is not part of it? I like patience and vigour being two of the virtues, which immediately implies an Aristotelian mean (which is always what is 'appropriate'). |