12 ideas
| 17610 | The Axiom of Choice paradoxically allows decomposing a sphere into two identical spheres [Maddy] |
| Full Idea: One feature of the Axiom of Choice that troubled many mathematicians was the so-called Banach-Tarski paradox: using the Axiom, a sphere can be decomposed into finitely many parts and those parts reassembled into two spheres the same size as the original. | |
| From: Penelope Maddy (Defending the Axioms [2011], 1.3) | |
| A reaction: (The key is that the parts are non-measurable). To an outsider it is puzzling that the Axiom has been universally accepted, even though it produces such a result. Someone can explain that, I'm sure. |
| 17620 | Critics of if-thenism say that not all starting points, even consistent ones, are worth studying [Maddy] |
| Full Idea: If-thenism denies that mathematics is in the business of discovering truths about abstracta. ...[their opponents] obviously don't regard any starting point, even a consistent one, as equally worthy of investigation. | |
| From: Penelope Maddy (Defending the Axioms [2011], 3.3) | |
| A reaction: I have some sympathy with if-thenism, in that you can obviously study the implications of any 'if' you like, but deep down I agree with the critics. |
| 17605 | Hilbert's geometry and Dedekind's real numbers were role models for axiomatization [Maddy] |
| Full Idea: At the end of the nineteenth century there was a renewed emphasis on rigor, the central tool of which was axiomatization, along the lines of Hilbert's axioms for geometry and Dedekind's axioms for real numbers. | |
| From: Penelope Maddy (Defending the Axioms [2011], 1.3) |
| 17625 | If two mathematical themes coincide, that suggest a single deep truth [Maddy] |
| Full Idea: The fact that two apparently fruitful mathematical themes turn out to coincide makes it all the more likely that they're tracking a genuine strain of mathematical depth. | |
| From: Penelope Maddy (Defending the Axioms [2011], 5.3ii) |
| 17615 | Every infinite set of reals is either countable or of the same size as the full set of reals [Maddy] |
| Full Idea: One form of the Continuum Hypothesis is the claim that every infinite set of reals is either countable or of the same size as the full set of reals. | |
| From: Penelope Maddy (Defending the Axioms [2011], 2.4 n40) |
| 17618 | Set-theory tracks the contours of mathematical depth and fruitfulness [Maddy] |
| Full Idea: Our set-theoretic methods track the underlying contours of mathematical depth. ...What sets are, most fundamentally, is markers for these contours ...they are maximally effective trackers of certain trains of mathematical fruitfulness. | |
| From: Penelope Maddy (Defending the Axioms [2011], 3.4) | |
| A reaction: This seems to make it more like a map of mathematics than the actual essence of mathematics. |
| 17614 | The connection of arithmetic to perception has been idealised away in modern infinitary mathematics [Maddy] |
| Full Idea: Ordinary perceptual cognition is most likely involved in our grasp of elementary arithmetic, but ...this connection to the physical world has long since been idealized away in the infinitary structures of contemporary pure mathematics. | |
| From: Penelope Maddy (Defending the Axioms [2011], 2.3) | |
| A reaction: Despite this, Maddy's quest is for a 'naturalistic' account of mathematics. She ends up defending 'objectivity' (and invoking Tyler Burge), rather than even modest realism. You can't 'idealise away' the counting of objects. I blame Cantor. |
| 16721 | Changes in secondary qualities are caused by changes in primary qualities [Giles of Orleans] |
| Full Idea: Every alteration in secondary qualities is caused by some alteration made in the primary qualities. | |
| From: Giles of Orleans (On 'Generation and Corruption' [1270], I.6c) | |
| A reaction: Pasnau calls this the 'supervenience' thesis, here with the addition of causation. Was this doctrine retained by Locke and Boyle? |
| 3488 | Freud treats the unconscious as intentional and hence mental [Freud, by Searle] |
| Full Idea: Freud thinks that our unconscious mental states exist as occurrent intrinsic intentional states even when unconscious. Their ontology is that of the mental, even when they are unconscious. | |
| From: report of Sigmund Freud (works [1900]) by John Searle - The Rediscovery of the Mind Ch. 7.V | |
| A reaction: Searle states this view in order to attack it. Whether such states are labelled as 'mental' seems uninteresting. Whether unconscious states can be intentional is crucial, and modern scientific understanding of the brain strongly suggest they can. |
| 5689 | Freud and others have shown that we don't know our own beliefs, feelings, motive and attitudes [Freud, by Shoemaker] |
| Full Idea: Freud persuaded many that beliefs, wishes and feelings are sometimes unconscious, and even sceptics about Freud acknowledge that there is self-deception about motive and attitudes. | |
| From: report of Sigmund Freud (works [1900]) by Sydney Shoemaker - Introspection p.396 | |
| A reaction: This seems to me obviously correct. The traditional notion is that the consciousness is the mind, but now it seems obvious that consciousness is only one part of the mind, and maybe even a peripheral (epiphenomenal) part of it. |
| 23950 | Freud said passions are pressures of some flowing hydraulic quantity [Freud, by Solomon] |
| Full Idea: Freud argued that the passions in general …were the pressures of a yet unknown 'quantity' (which he simply designated 'Q'). He first thought this flowed through neurones, …and always couched the idea in the language of hydraulics. | |
| From: report of Sigmund Freud (works [1900]) by Robert C. Solomon - The Passions 3.4 | |
| A reaction: This is the main target of Solomon's criticism, because its imagery has become so widespread. It leads to talk of suppressing emotions, or sublimating them. However, it is not too different from Nietzsche's 'drives' or 'will to power'. |
| 22344 | Freud is pessimistic about human nature; it is ambivalent motive and fantasy, rather than reason [Freud, by Murdoch] |
| Full Idea: Freud takes a thoroughly pessimistic view of human nature. ...Introspection reveals only the deep tissue of ambivalent motive, and fantasy is a stronger force than reason. Objectivity and unselfishness are not natural to human beings. | |
| From: report of Sigmund Freud (works [1900], II) by Iris Murdoch - The Sovereignty of Good II | |
| A reaction: Interesting. His view seems to have coloured the whole of modern culture, reinforced by the hideous irrationality of the Nazis. Adorno and Horkheimer attacking the Enlightenment was the last step in that process. |