| 1504 | Something must be unchanging to make recognition and knowledge possible [Aristotle on Parmenides] |
| Full Idea: Parmenides and Melissus were the first to appreciate that there must be unchanging entities, if recognition and knowledge are to exist. | |
| From: comment on Parmenides (fragments/reports [c.474 BCE], A25) by Aristotle - On the Heavens 298b14 |
| 12503 | Identity means that the idea of a thing remains the same over time [Locke] |
| Full Idea: In this consists identity, when the ideas a thing is attributed to vary not at all from what they were at that moment, wherein we consider their former existence, and to which we compare the present. | |
| From: John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.24.01) | |
| A reaction: Since we recognise that we might, in odd circumstances, have the identical idea while the object has been swapped, this is wrong. It sounds like the identity of indiscernibles. Identity is a concept applied to reality, not to ideas. |
| 13182 | Changeable accidents are modifications of unchanging essences [Leibniz] |
| Full Idea: Everything accidental or changeable ought to be a modification of something essential or perpetual. | |
| From: Gottfried Leibniz (Letters to Burcher De Volder [1706], 1704.06.30) | |
| A reaction: Clear evidence that Leibniz is very much a traditional Aristotelian essentialist, and not as modal logicians tend to characterise him, as a super-essentialist who thinks all properties are essential. They are necessary for identity, but that's different. |
| 21299 | Changing a part can change the whole, not absolutely, but by its proportion of the whole [Hume] |
| Full Idea: Though the change of any considerable part of a mass of matter destroys the identity of the whole, yet we must measure the greatness of the part, not absolutely, but by its proportion to the whole. | |
| From: David Hume (Treatise of Human Nature [1739], I.IV.6) | |
| A reaction: This seems to nicely demonstrate that the wholeness is in the mind of the perceiver, and does not simply depend on objective facts. Compare the proportion needed to change my pile of mud and my pile of gold. |
| 21300 | A change more obviously destroys an identity if it is quick and observed [Hume] |
| Full Idea: A change in any considerable part of a body destroys its identity; but 'tis remarkable that where the change is produced gradually and insensibly we are less apt to ascribe to it the same effect. | |
| From: David Hume (Treatise of Human Nature [1739], I.IV.6) | |
| A reaction: Broad spotted that landscapes change too, but so slowly that we barely admit any change at all. The type of change also matters. If my car slowly changes to chocolate the speed of change is a minor factor. |
| 1350 | Continuity is needed for existence, otherwise we would say a thing existed after it ceased to exist [Reid] |
| Full Idea: Identity supposes an uninterrupted continuance of existence….Otherwise we must suppose a being to exist after it has ceased to exist, and to have existed before it was produced, which are manifest contradictions. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: I take the point to be that if something is supposed to survive a gap in its existence, that must imply that it somehow exists during the gap. If a light flashes on and off, is it really a new entity each time? |
| 5626 | An a priori principle of persistence anticipates all experience [Kant] |
| Full Idea: The principle of persistence is one that anticipates experience just as much as that of causality. | |
| From: Immanuel Kant (Critique of Pure Reason [1781], B795/A767) | |
| A reaction: This is the notion that identity is an indefinable basic of our understanding. He is objecting to Hume, who, of course, thought persistance was just an experience. Personally I persistance to be a posteriori, but how else could things exist? |
| 16991 | No one seems to know the identity conditions for a material object (or for people) over time [Kripke] |
| Full Idea: Adequate necessary and sufficient conditions for identity which do not beg the question are very rare. …I don't know of such conditions for identity of material objects over time, or for people. Everyone knows what a problem this is. | |
| From: Saul A. Kripke (Naming and Necessity lectures [1970], Lecture 1) | |
| A reaction: Typical of Kripke, who only seems to commit to conclusions suggested to him by his modal logic, and is baffled by almost everything else. I think one can at least attempt an essentialist approach to this problem. |
| 16503 | 'What is it?' gives the kind, nature, persistence conditions and identity over time of a thing [Wiggins] |
| Full Idea: The question 'what is it?' refers to the persistence and lifespan of an entity, and so manifests the identity over time of an entity and its persistence, between persistence and existence, and between its existence and being the kind of thing it is. | |
| From: David Wiggins (Sameness and Substance [1980], 2.1) | |
| A reaction: The idea that establishing the kind of a thing can do all this work strikes me as false. The lifespan of a 'human' can be between five minutes and a hundred years. Humans have a clear death, but thunderstorms don't. |
| 9663 | A thing 'perdures' if it has separate temporal parts, and 'endures' if it is wholly present at different times [Lewis] |
| Full Idea: Something 'perdures' iff it persists by having different temporal parts, or stages, at different times, though no one part of it is wholly present at more than one time; whereas it 'endures' iff it persists by being wholly present at more than one time. | |
| From: David Lewis (On the Plurality of Worlds [1986], 4.2) | |
| A reaction: Only a philosopher would come up with a concept like perdurance. I'm thinking about this one, and will get back to you in a later-numbered idea... He compares perdurance to the way a road persists through space. |
| 16025 | If things change they become different - but then no one thing undergoes the change! [Gallois] |
| Full Idea: If things really change, there can't literally be one thing before and after the change. However, if there isn't one thing before and after the change, then no thing has really undergone any change. | |
| From: André Gallois (Identity over Time [2011], Intro) | |
| A reaction: [He cites Copi for this way of expressing the problem of identity through change] There is an obvious simple ambiguity about 'change' in ordinary English. A change of property isn't a change of object. Painting a red ball blue isn't swapping it. |
| 16233 | Gallois hoped to clarify identity through time, but seems to make talk of it impossible [Hawley on Gallois] |
| Full Idea: A problem for Gallois is that he leaves us no way to talk about questions of genuine identity through time, and thus undercuts one motivation for his own position. | |
| From: comment on André Gallois (Occasions of Identity [1998]) by Katherine Hawley - How Things Persist 5.8 | |
| A reaction: Gallois seems to need a second theory of identity to support his Occasional Identity theory. Two things need an identity each, before we can say that the two identities coincide. (Time to read Gallois!) |
| 14958 | A continuous object might be a type, with instances at each time [Ladyman/Ross] |
| Full Idea: Why should not 'Napoleon' be a type, of which 'Napoleon in 1805' and 'Napoleon in 1813' are instances? | |
| From: J Ladyman / D Ross (Every Thing Must Go [2007], 5.6) | |
| A reaction: That is very nice. That might be a view that suits presentism, where the timed instances never co-exist, and so have the sort of abstract existence that we associate with types. |
| 15396 | Most criteria for identity over time seem to leave two later objects identical to the earlier one [Cameron] |
| Full Idea: Criteria for identity across times have proven hard to give. Whatever criteria we lay down, it seems that there are possible situations in which two later objects bear the relevant relation to one earlier object, though only one of them can be identical. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Personal') | |
| A reaction: We only have to think of twins, amoebae that fission, and the Ship of Theseus. We seem to end up inventing a dubious criterion in order to break the tie. |
| 22612 | Endurance and perdurance just show the consequences of A or B series time [Ingthorsson] |
| Full Idea: Endurance and perdurance are not explanations, but are merely characterisations of persistance with the constraints imposed by either an A or a B view of time. | |
| From: R.D. Ingthorsson (A Powerful Particulars View of Causation [2021], 2.1) | |
| A reaction: This is 3-D asnd 4-D objects. A simple and illuminating observation. I love reading broad brush books that make all these simple connections between what seem isolated theories in philosophy. These links are the heart of the subject. |
| 22625 | Science suggests causal aspects of the constitution and persistance of objects [Ingthorsson] |
| Full Idea: There are very obvious causal aspects to the constitution and continued existence of compound entities, especially in light of the scientific image of the world. | |
| From: R.D. Ingthorsson (A Powerful Particulars View of Causation [2021], 6) | |
| A reaction: I like this a lot. He aims to explain constitution and persistance, rather than just describing or characterising them, and causal binding seems the obvious thought. There are still intermittent and distributed objects, like a dismantled clock. |