11 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. |
| 21226 | Husserl sees the ego as a monad, unifying presence, sense and intentional acts [Husserl, by Velarde-Mayol] |
| Full Idea: Husserl's notion of monad expresses a complete inegration of every intentional presence into its sense, and every sense into the intentional acts, ....and finally every intentional act is integrated into the ego. | |
| From: report of Edmund Husserl (Cartesian Meditations [1931]) by Victor Velarde-Mayol - On Husserl 4.6.2 | |
| A reaction: No, I don't understand that either, but it makes good sense to employ the concept of a 'monad' into the concept of the ego, if you think it embodies perfect unity. That was a main motivation for Leibniz to employ the word. |
| 21228 | Husserl's monads (egos) communicate, through acts of empathy. [Husserl, by Velarde-Mayol] |
| Full Idea: For Husserl monads have windows because they communicate with each other. The windows of the monads are the acts of empathy. | |
| From: report of Edmund Husserl (Cartesian Meditations [1931]) by Victor Velarde-Mayol - On Husserl 4.7.5 | |
| A reaction: Leibniz said his monads (which include minds) have 'no windows'. The mere existence of empathy (or mirror neurons, as we would say) is hardly sufficient to defeat solipsism. |
| 21225 | The psychological ego is worldly, and the pure ego follows transcendental reduction [Husserl, by Velarde-Mayol] |
| Full Idea: Husserl distinguishes two sorts of egos or subjects of experience, the psychological ego and the pure ego. The psychological ego is a reality of the world, and the pure ego is a result of transcendental reduction. | |
| From: report of Edmund Husserl (Cartesian Meditations [1931]) by Victor Velarde-Mayol - On Husserl 4.6.1 | |
| A reaction: The sounds like embracing both the Cartesian and the Kantian egos. This is obviously the source of Sartre's interesting early book on the self. 'Transcendental reduction' is his bracketing or epoché. |
| 23261 | A people, not government, creates a constitution, which is essential for legitimacy [Paine] |
| Full Idea: A constitution is not the act of a government, but of a people constituting a government, and a government without a constitution is power without right. | |
| From: Thomas Paine (Rights of Man [1792], Ch.7), quoted by A.C. Grayling - The Good State 5 | |
| A reaction: A constitution looks like the ultimate focus of a social contract (though Greeks had them long ago). It is hard to say why a government should consider itself to be sovereign if it hasn't got it in writing. |