17 ideas
18812 | Split out the logical vocabulary, make an assignment to the rest. It's logical if premises and conclusion match [Tarski, by Rumfitt] |
Full Idea: Tarski made a division of logical and non-logical vocabulary. He then defined a model as a non-logical assignment satisfying the corresponding sentential function. Then a conclusion follows logically if every model of the premises models the conclusion. | |
From: report of Alfred Tarski (The Concept of Logical Consequence [1936]) by Ian Rumfitt - The Boundary Stones of Thought 3.2 | |
A reaction: [compressed] This is Tarski's account of logical consequence, which follows on from his account of truth. 'Logical validity' is then 'true in every model'. Rumfitt doubts whether Tarski has given the meaning of 'logical consequence'. |
13344 | X follows from sentences K iff every model of K also models X [Tarski] |
Full Idea: The sentence X follows logically from the sentences of the class K if and only if every model of the class K is also a model of the sentence X. | |
From: Alfred Tarski (The Concept of Logical Consequence [1936], p.417) | |
A reaction: [see Idea 13343 for his account of a 'model'] He is offering to define logical consequence in general, but this definition fits what we now call 'semantic consequence', written |=. This it is standard practice to read |= as 'models'. |
13343 | A 'model' is a sequence of objects which satisfies a complete set of sentential functions [Tarski] |
Full Idea: An arbitrary sequence of objects which satisfies every sentential function of the sentences L' will be called a 'model' or realization of the class L of sentences. There can also be a model of a single sentence is this way. | |
From: Alfred Tarski (The Concept of Logical Consequence [1936], p.417) | |
A reaction: [L' is L with the constants replaced by variables] Tarski is the originator of model theory, which is central to modern logic. The word 'realization' is a helpful indicator of what he has in mind. A model begins to look like a possible world. |
16705 | Whiteness isn't created in an alteration, because it is just this-being-white [Oresme] |
Full Idea: If it is said that whiteness begins to be through alteration, this does not hold, because whiteness is nothing other than this-being-white. | |
From: Nicole Oresme (On 'Generation and Corruption' [1349], I.2), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 19.3 | |
A reaction: This innocent-looking remark is dynamite, because it rejects the separability of qualities, which threatens the doctrine of Transubstantiation. |
4608 | Minds are hard-wired, or trial-and-error, or experimental, or full self-aware [Dennett, by Heil] |
Full Idea: Dennett identifies a hierarchy of minds running from 'Darwinian' (hard-wired solutions to problems), to 'Skinnerian' (trial-and-error), to 'Popperian' (anticipating possible experience), to 'Gregorian' (self-conscious representation, probably linguistic). | |
From: report of Daniel C. Dennett (Kinds of Minds [1996]) by John Heil - Philosophy of Mind Ch.5 | |
A reaction: Interesting. The concept of an experiment seems a major step (assessing reality against an internal map), and the ability to think about one's own thoughts certainly strikes me as the mark of a top level mind. Maybe that is the importance of language. |
4880 | Sentience comes in grades from robotic to super-human; we only draw a line for moral reasons [Dennett] |
Full Idea: 'Sentience' comes in every imaginable grade or intensity, from the simplest and most 'robotic', to the most exquisitely sensitive, hyper-reactive 'human'. We have to draw a line for moral policy, but it is unlikely we will ever discover a threshold. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.4) | |
A reaction: This is the only plausible view, if you take the theory of evolution seriously. We can even observe low-grade marginal sentience in our own minds, and then shoot up the scale when we focus our minds properly on an object. |
4873 | What is it like to notice an uncomfortable position when you are asleep? [Dennett] |
Full Idea: What is it like to notice, while sound asleep, that your left arm has become twisted into a position in which it is putting undue strain on your left shoulder? Like nothing. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.1) | |
A reaction: A nice question, and all part of Dennett's accurate campaign to show that consciousness is not an all-or-nothing thing. As when we are barely aware of driving, innumerable things happen in the shadowy corners of thought. |
4881 | Being a person must involve having second-order beliefs and desires (about beliefs and desires) [Dennett] |
Full Idea: An important step towards becoming a person is the step up from a first-order intentional system to a second-order system (which has beliefs and desires about beliefs and desires). | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.5) | |
A reaction: Call it 'meta-thought'. I agree. Dennett thinks language is crucial to this, but the hallmark of intelligence and full-blown personhood is meta- and meta-meta-thought. Maybe the development of irony is a step up the evolutionary scale. Sarcasm is GOOD. |
4875 | We descend from robots, and our intentionality is composed of billions of crude intentional systems [Dennett] |
Full Idea: We are descended from robots, and composed of robots, and all the intentionality we enjoy is derived from the more fundamental intentionality of billions of crude intentional systems. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.2) | |
A reaction: A more grand view of intentionality (such as Searle's) seems more attractive than this, but the crucial fact about Dennett is that he takes the implications of evolution much more seriously than other philosophers. He's probably right. |
4879 | There is no more anger in adrenaline than silliness in a bottle of whiskey [Dennett] |
Full Idea: There is no more fear or anger in adrenaline than there is silliness in a bottle of whiskey. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.3) | |
A reaction: Not exactly an argument, but a nice rhetorical point against absurd claims about identity and reduction and elimination. We may say that there is no fear without adrenaline, and no adrenaline in a live brain without fear. |
4876 | Maybe there is a minimum brain speed for supporting a mind [Dennett] |
Full Idea: Perhaps there is a minimum speed for a mind, rather like the minimum escape velocity required to overcome gravity and leave the planet. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.3) | |
A reaction: Dennett rejects this speculation, but he didn't stop to imagine what it would be LIKE if your brain slowed down, and he never considers Edelman's view that mind is a process. Put the two together… |
4878 | The materials for a mind only matter because of speed, and a need for transducers and effectors [Dennett] |
Full Idea: I think there are only two good reasons why, when you make a mind, the materials matter: speed, and the ubiquity of transducers and effectors throughout the nervous system. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.3) | |
A reaction: This sounds roughly right, because it gives you something between multiple realisability (minds made of cans and string), and type-type identity (minds ARE a particular material). Call it 'biological functionalism'? |
4874 | The predecessor and rival of the language of thought hypothesis is the picture theory of ideas [Dennett] |
Full Idea: The ancestor and chief rival of the language-of-thought hypothesis is the picture theory of ideas - that thoughts are about what they are about because they resemble their objects. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.2) | |
A reaction: When you place them side by side, neither seems quite right. How can a mental state resemble an object, and how can an inner language inherently capture the features of an object? Maybe we lack the words for the correct theory. |
4882 | Concepts are things we (unlike dogs) can think about, because we have language [Dennett] |
Full Idea: A dog cannot consider its concepts. Concepts are not things in a dog's world in the way that cats are. Concepts are things in our world, because we have language. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.6) | |
A reaction: Dogs must have concepts, though, or much of their behaviour (like desperation to go for a walk, or to eat) is baffling. This is as good a proposal as I have ever encountered for the value of language. Meta-thought is a huge evolutionary advantage. |
13345 | Sentences are 'analytical' if every sequence of objects models them [Tarski] |
Full Idea: A class of sentences can be called 'analytical' if every sequence of objects is a model of it. | |
From: Alfred Tarski (The Concept of Logical Consequence [1936], p.418) | |
A reaction: See Idea 13344 and Idea 13343 for the context of this assertion. |
4872 | Most people see an abortion differently if the foetus lacks a brain [Dennett] |
Full Idea: If a fetus that is being considered for abortion is known to be anencephalic (lacking a brain), this dramatically changes the issue for most people, though not for all. | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.1) | |
A reaction: A very effective point, as it is hard to see what grounds could be given for not aborting in this case. But the brain then clearly becomes the focus of why abortion is often rejected by many people. |
4877 | Maybe plants are very slow (and sentient) animals, overlooked because we are faster? [Dennett] |
Full Idea: Might plants just be 'very slow animals', enjoying sentience that has been overlooked by us because of our human timescale chauvinism? | |
From: Daniel C. Dennett (Kinds of Minds [1996], Ch.3) | |
A reaction: Delightful thought, arising from pondering the significance of the speed of operation of the brain. I think it is false, because I think high speed is essential to mind, and Dennett seems not to. |