16 ideas
| 8859 | The main modal logics disagree over three key formulae [Yablo] |
| Full Idea: Lewis's different systems of modal logic differed about such formulae as □P implies □□P; ◊□P implies □P; and ◊S implies □◊S | |
| From: Stephen Yablo (Apriority and Existence [2000], §06) | |
| A reaction: Yablo's point is that the various version don't seem to make much difference to our practices in logic, mathematics and science. The problem, says Yablo, is deciding exactly what you mean by 'necessarily' and 'possibly'. |
| 13430 | Infinity: there is an infinity of distinguishable individuals [Ramsey] |
| Full Idea: The Axiom of Infinity means that there are an infinity of distinguishable individuals, which is an empirical proposition. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], §5) | |
| A reaction: The Axiom sounds absurd, as a part of a logical system, but Ramsey ends up defending it. Logical tautologies, which seem to be obviously true, are rendered absurd if they don't refer to any objects, and some of them refer to infinities of objects. |
| 13428 | Reducibility: to every non-elementary function there is an equivalent elementary function [Ramsey] |
| Full Idea: The Axiom of Reducibility asserted that to every non-elementary function there is an equivalent elementary function [note: two functions are equivalent when the same arguments render them both true or both false]. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], §2) | |
| A reaction: Ramsey in the business of showing that this axiom from Russell and Whitehead is not needed. He says that the axiom seems to be needed for induction and for Dedekind cuts. Since the cuts rest on it, and it is weak, Ramsey says it must go. |
| 13427 | Either 'a = b' vacuously names the same thing, or absurdly names different things [Ramsey] |
| Full Idea: In 'a = b' either 'a' and 'b' are names of the same thing, in which case the proposition says nothing, or of different things, in which case it is absurd. In neither case is it an assertion of a fact; it only asserts when a or b are descriptions. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], §1) | |
| A reaction: This is essentially Frege's problem with Hesperus and Phosphorus. How can identities be informative? So 2+2=4 is extensionally vacuous, but informative because they are different descriptions. |
| 13334 | Contradictions are either purely logical or mathematical, or they involved thought and language [Ramsey] |
| Full Idea: Group A consists of contradictions which would occur in a logical or mathematical system, involving terms such as class or number. Group B contradictions are not purely logical, and contain some reference to thought, language or symbolism. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], p.171), quoted by Graham Priest - The Structure of Paradoxes of Self-Reference 1 | |
| A reaction: This has become the orthodox division of all paradoxes, but the division is challenged by Priest (Idea 13373). He suggests that we now realise (post-Tarski?) that language is more involved in logic and mathematics than we thought. |
| 8865 | If 'the number of Democrats is on the rise', does that mean that 50 million is on the rise? [Yablo] |
| Full Idea: If someone says 'the number of Democrats is on the rise', he or she wants to focus on Democrats, not numbers. If the number is 50 million, is 50 million really on the rise? | |
| From: Stephen Yablo (Apriority and Existence [2000], §14) | |
| A reaction: This is a very nice warning from Yablo, against easy platonism, or any sort of platonism at all. We routinely say that numbers are 'increasing', but the real meaning needs entangling. Here it refers to people joining a party. |
| 8863 | We must treat numbers as existing in order to express ourselves about the arrangement of planets [Yablo] |
| Full Idea: It is only by making as if to countenance numbers that one can give expression in English to a fact having nothing to do with numbers, a fact about stars and planets and how they are numerically proportioned. | |
| From: Stephen Yablo (Apriority and Existence [2000], §13) | |
| A reaction: To avoid the phrase 'numerically proportioned', he might have alluded to the 'pattern' of the stars and planets. I'm not sure which -ism this is, but it seems to me a good approach. The application is likely to precede the theory. |
| 13426 | Formalists neglect content, but the logicists have focused on generalizations, and neglected form [Ramsey] |
| Full Idea: The formalists neglected the content altogether and made mathematics meaningless, but the logicians neglected the form and made mathematics consist of any true generalisations; only by taking account of both sides can we obtain an adequate theory. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], §1) | |
| A reaction: He says mathematics is 'tautological generalizations'. It is a criticism of modern structuralism that it overemphasises form, and fails to pay attention to the meaning of the concepts which stand at the 'nodes' of the structure. |
| 13425 | Formalism is hopeless, because it focuses on propositions and ignores concepts [Ramsey] |
| Full Idea: The hopelessly inadequate formalist theory is, to some extent, the result of considering only the propositions of mathematics and neglecting the analysis of its concepts. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], §1) | |
| A reaction: You'll have to read Ramsey to see how this thought pans out, but it at least gives a pointer to how to go about addressing the question. |
| 8862 | Platonic objects are really created as existential metaphors [Yablo] |
| Full Idea: The means by which platonic objects are simulated is existential metaphor. Numbers are conjured up as metaphorical measures of cardinality. | |
| From: Stephen Yablo (Apriority and Existence [2000], §12) | |
| A reaction: 'Fictional' might be a better word than 'metaphorical', since the latter usually implies some sort of comparison. |
| 8864 | We quantify over events, worlds, etc. in order to make logical possibilities clearer [Yablo] |
| Full Idea: It is not that the contents of sentences are inexpressible without quantifying over events, worlds, etc. (they aren't). But the logical relations become much more tractable if we represent them quantificationally. | |
| From: Stephen Yablo (Apriority and Existence [2000], §13) | |
| A reaction: Yablo is explaining why we find ourselves committed to abstract objects. It is essentially, as I am beginning to suspect, a conspiracy of logicians. What on earth is 'the empty set' when it is at home? What's it made of? |
| 8858 | Philosophers keep finding unexpected objects, like models, worlds, functions, numbers, events, sets, properties [Yablo] |
| Full Idea: There's a tradition in philosophy of finding 'unexpected objects' in truth-conditions, such as countermodels, possible worlds, functions, numbers, events, sets and properties. | |
| From: Stephen Yablo (Apriority and Existence [2000], §02) | |
| A reaction: This is a very nice perspective on the whole matter of abstract objects. If we find ourselves reluctantly committed to the existence of something which is ontologically peculiar, we should go back to the philosophical drawing-board. |
| 22328 | I just confront the evidence, and let it act on me [Ramsey] |
| Full Idea: I can but put the evidence before me, and let it act on my mind. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], p.202), quoted by Michael Potter - The Rise of Analytic Philosophy 1879-1930 70 'Deg' | |
| A reaction: Potter calls this observation 'downbeat', but I am an enthusiastic fan. It is roughly my view of both concept formation and of knowledge. You soak up the world, and respond appropriately. The trick is in the selection of evidence to confront. |
| 22325 | A belief is knowledge if it is true, certain and obtained by a reliable process [Ramsey] |
| Full Idea: I have always said that a belief was knowledge if it was 1) true, ii) certain, iii) obtained by a reliable process. | |
| From: Frank P. Ramsey (The Foundations of Mathematics [1925], p.258), quoted by Michael Potter - The Rise of Analytic Philosophy 1879-1930 66 'Rel' | |
| A reaction: Not sure why it has to be 'certain' as well as 'true'. It seems that 'true' is objective, and 'certain' subjective. I think I know lots of things of which I am not fully certain. Reliabilism long preceded Alvin Goldman. |
| 8861 | Hardly a word in the language is devoid of metaphorical potential [Yablo] |
| Full Idea: There is hardly a word in the language - be it an adverb, preposition, conjunction, or what have you - that is devoid of metaphorical potential. | |
| From: Stephen Yablo (Apriority and Existence [2000], §12) | |
| A reaction: Yablo goes on to claim that metaphor is at the heart of all of our abstract thinking. 'Dead metaphors' (like the "mouth" of a river) sink totally into literal language. I think Yablo is on the right lines. |
| 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'). |