8 ideas
| 6021 | It is only when we say a proposition that we speak truly or falsely [Sext.Empiricus] |
| Full Idea: It is only when we say a proposition that we speak truly or falsely. | |
| From: Sextus Empiricus (Against the Professors (six books) [c.180], 8.74) | |
| A reaction: This makes assertions truth-bearers, rather than propositions. But a proposition can be true or false if it is stamped with a date and/or place. "Shakespeare was born in Stratford on 23rd April 1664". No one needs to assert that. |
| 9879 | NF has no models, but just blocks the comprehension axiom, to avoid contradictions [Quine, by Dummett] |
| Full Idea: Quine's New Foundations system of set theory, devised with no model in mind, but on the basis of a hunch that a purely formal restriction on the comprehension axiom would block all contradictions. | |
| From: report of Willard Quine (New Foundations for Mathematical Logic [1937]) by Michael Dummett - Frege philosophy of mathematics Ch.18 | |
| A reaction: The point is that Quine (who had an ontological preference for 'desert landscapes') attempted to do without an ontological commitment to objects (and their subsequent models), with a purely formal system. Quine's NF is not now highly regarded. |
| 6020 | 'Man is a rational mortal animal' is equivalent to 'if something is a man, that thing is a rational mortal animal' [Sext.Empiricus] |
| Full Idea: Definitions are identical to universal propositions in meaning, and only differ in syntax, for whoever says 'Man is a rational mortal animal' says the same thing in meaning as whoever says 'If something is a man, that thing is a rational mortal animal'. | |
| From: Sextus Empiricus (Against the Professors (six books) [c.180], 11.8) | |
| A reaction: How strikingly like Bertrand Russell's interest and solutions. Sextus shows a straightforward interest in logical form, of a kind we associate with the twentieth century. Did Sextus Empiricus invent quantification? |
| 6026 | How can you investigate without some preconception of your object? [Sext.Empiricus] |
| Full Idea: A preconception and conception must precede every object of investigation, for how can anyone even investigate without some conception of the object of investigation? | |
| From: Sextus Empiricus (Against the Professors (six books) [c.180], 8.331a) | |
| A reaction: The Duhem-Quine thesis about the 'theory-ladenness of observation' is just a revival of some routine ancient scepticism. As well as a conceptual scheme to accommodate the observation, there must also be some motivation for the investigation. |
| 7861 | Libet says the processes initiated in the cortex can still be consciously changed [Libet, by Papineau] |
| Full Idea: Libet himself points out that the conscious decisions still have the power to 'endorse' or 'cancel', so to speak, the processes initiated by the earlier cortical activity: no action will result if the action's execution is consciously countermanded. | |
| From: report of Benjamin Libet (Unconscious Cerebral Initiative [1985]) by David Papineau - Thinking about Consciousness 1.4 | |
| A reaction: This is why Libet's findings do not imply 'epiphenomenalism'. It seems that part of a decisive action is non-conscious, undermining the all-or-nothing view of consciousness. Searle tries to smuggle in free will at this point (Idea 3817). |
| 6660 | Libet found conscious choice 0.2 secs before movement, well after unconscious 'readiness potential' [Libet, by Lowe] |
| Full Idea: Libet found that a subject's conscious choice to move was about a fifth of a second before movement, and thus later than the onset of the brain's so-called 'readiness potential', which seems to imply that unconscious processes initiates action. | |
| From: report of Benjamin Libet (Unconscious Cerebral Initiative [1985]) by E.J. Lowe - Introduction to the Philosophy of Mind Ch.9 | |
| A reaction: Of great interest to philosophers! It seems to make conscious choices epiphenomenal. The key move, I think, is to give up the idea of consciousness as being all-or-nothing. My actions are still initiated by 'me', but 'me' shades off into unconsciousness. |
| 6032 | Right actions, once done, are those with a reasonable justification [Sext.Empiricus] |
| Full Idea: Right action is whatever, once it has been done, has a reasonable justification. | |
| From: Sextus Empiricus (Against the Professors (six books) [c.180], 7.158) | |
| A reaction: Why does he add 'once it has been done'? Wouldn't a proposed action be right if it had a reasonable justification? This grows out of the classical and Stoic emphasis on reason in ethics, and leads towards Scanlon's Contractualism. |
| 1517 | The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature' [Sext.Empiricus] |
| Full Idea: The tektraktys (1+2+3+4=10) is the 'fount of ever-flowing nature', because nature is a harmony of three concords (4th,5th and octave), and these ratios (4:3, 3:2, and 2:1) are found in the tektraktys. | |
| From: Sextus Empiricus (Against the Professors (six books) [c.180], 7.95) |