11 ideas
| 18004 | We can't do philosophy without knowledge of types and categories [Ryle] |
| Full Idea: We are in the dark about the nature of philosophical problems and methods if we are in the dark about types and categories. | |
| From: Gilbert Ryle (Categories [1938], p.189), quoted by Ofra Magidor - Category Mistakes 1.2 | |
| A reaction: Magidor and others take this to be an assertion about language and logic, but I take it to be an assertion about reality. It is an early assertion of Schaffer's claim that ontology concerns the structure of existence, and not just what exists. |
| 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. |
| 21677 | How can the not-true fail to be false, or the not-false fail to be true? [Cicero] |
| Full Idea: How can something that is not true not be false, or how can something that is not false not be true? | |
| From: M. Tullius Cicero (On Fate ('De fato') [c.44 BCE], 16.38) | |
| A reaction: We must at least distinguish between whether the contrary thing is not actually true, or whether we are prepared to assert that it is not true. The disjunction may seem to be a false dichotomy. 'He isn't good' may not entail 'he is evil'. |
| 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. |
| 21667 | Oratory and philosophy are closely allied; orators borrow from philosophy, and ornament it [Cicero] |
| Full Idea: There is a close alliance between the orator and the philosophical system of which I am a follower, since the orator borrows subtlely from the Academy, and repays the loan by giving to it a copious and flowing style and rhetorical ornament. | |
| From: M. Tullius Cicero (On Fate ('De fato') [c.44 BCE], 02.03) | |
| A reaction: It is a misundertanding to think that rhetoric and philosophy are seen as in necessary opposition. Philosophers just seemed to think that oratory works a lot better if it is truthful. |
| 21678 | If desire is not in our power then neither are choices, so we should not be praised or punished [Cicero] |
| Full Idea: If the cause of desire is not situated within us, even desire itself is also not in our power. ...It follows that neither assent nor action is in our power. Hence there is no justice in either praise or blame, either honours or punishments. | |
| From: M. Tullius Cicero (On Fate ('De fato') [c.44 BCE], 17.40) | |
| A reaction: This is the view of 'old philosophers', but I'm unsure which ones. Cicero spurns this view. It is obvious that the causes of our desires are largely out of our control. Responsibility seems to concern what we do about our desires. |