| 11380 | Two things with the same primary being and essence are one thing [Aristotle] |
| Full Idea: If any two items have a single substance [ousia, primary being] and a single what-it-is-to-be-that-thing [to ti en einai, essence], then they are themselves a single thing. | |
| From: Aristotle (Metaphysics [c.324 BCE], 1038b14) | |
| A reaction: [alternative translations by Vasilis Politis] This isn't quite the identity of indiscernibles, because it allows superficial identity along with deep difference (H2O and XYZ, for example, or jadeite and nephrite). |
| 22143 | Identity does not exclude possible or imagined difference [Suárez, by Boulter] |
| Full Idea: To be really the same excludes being really other, but does not exclude being other modally or mentally. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], 7.65) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: So the statue and the clay are identical, but they could become separate, or be imagined as separate. |
| 22146 | Minor Real distinction: B needs A, but A doesn't need B [Suárez, by Boulter] |
| Full Idea: The Minor Real distinction is if A can exist without B, but B ceases to exist without A. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: This is one-way independence. Boulter's example is Peter and Peter's actual weight. |
| 22145 | Major Real distinction: A and B have independent existences [Suárez, by Boulter] |
| Full Idea: The Major Real distinction is if A can exist in the real order without B, and B can exist in the real order without A. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: Boulter's example is the distinction between Peter and Paul, where their identity of kind is irrelevant. This is two-way independence. |
| 22144 | Real Essential distinction: A and B are of different natural kinds [Suárez, by Boulter] |
| Full Idea: The Real Essential distinction says if A and B are not of the same natural kind, then they are essentially distinct. This is the highest degree of distinction. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: Boulter says Peter is essentially distinct from a cabbage, because neither has the nature of the other. |
| 22147 | Conceptual/Mental distinction: one thing can be conceived of in two different ways [Suárez, by Boulter] |
| Full Idea: The Conceptual or Mental distinction is when A and B are actually identical but we have two different ways of conceiving them. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: This is the Morning and Evening Star. I bet Frege never read Suarez. This seems to be Spinoza's concept of mind/body. |
| 22148 | Modal distinction: A isn't B or its property, but still needs B [Suárez, by Boulter] |
| Full Idea: The Modal distinction is when A is not B or a property of B, but still could not possibly exist without B. | |
| From: report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4 | |
| A reaction: Duns Scotus proposed in, Ockham rejected it, but Suarez supports it. Suarez proposes that light's dependence on the Sun is distinct from the light itself, in this 'modal' way. |
| 19394 | Inequality can be brought infinitely close to equality [Leibniz] |
| Full Idea: Equality may be considered as an infinitely small inequality, and we may make inequality approach equality as much as we wish. | |
| From: Gottfried Leibniz (A General Principle to Explain Laws of Nature [1687], p.67) | |
| A reaction: An interesting response to David Lewis's brusque dismissal of the problem of identity, as all-or-nothing...end of story. |
| 1207 | Both number and unity are incompatible with the relation of identity [Hume] |
| Full Idea: Both number and unity are incompatible with the relation of identity. | |
| From: David Hume (Treatise of Human Nature [1739], I.IV.2) |
| 21290 | Multiple objects cannot convey identity, because we see them as different [Hume] |
| Full Idea: A mutiplicity of objects can never convey the idea of identity. The mind always pronounces the one not to be the other. | |
| From: David Hume (Treatise of Human Nature [1739], I.IV.2) | |
| A reaction: However, if we are talking on the phone about two objects we are viewing, such as two buildings, our descriptions might lead us to conclude that our objects are identical. Thus experience might imply identity. |
| 11874 | Real identity admits of no degrees [Reid] |
| Full Idea: Wherever identity is real, it admits of no degrees. | |
| From: Thomas Reid (Essays on Intellectual Powers 5: Abstraction [1785]), quoted by David Wiggins - Sameness and Substance Renewed 6 epig | |
| A reaction: Wiggins quotes this with strong approval. Personally I am inclined to think that identity may admit of no degrees in human thought, because that is the only way we can do it, but the world is full of uncertain identities, at every level. |
| 21320 | Identity is familiar to common sense, but very hard to define [Reid] |
| Full Idea: Every man of common sense has a clear and distinct notion of identity. If you ask for a definition of identity, I confess I can give none. It is too simple a notion. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 4) | |
| A reaction: 'Identical' seems to be a two-place predicate, but the only strict way two things can be identical is if there is actually just one thing. In which case just drop the word 'identity' (instead of defining it), and say there is just one thing here. |
| 1367 | Identity can only be affirmed of things which have a continued existence [Reid] |
| Full Idea: Identity can only be affirmed of things which have a continued existence. | |
| From: Thomas Reid (Essays on Intellectual Powers 3: Memory [1785], III.Ch 6) | |
| A reaction: This doesn't mean that Reid thinks there is nothing more to the identity than their similitude. But he, like Hume, denies that there is personal identity at any given instant. Reid is better at criticism than at formulating his own theory. |
| 16022 | The idea of a criterion of identity was introduced by Frege [Frege, by Noonan] |
| Full Idea: The notion of a criterion of identity was introduced into philosophical terminology in Frege's 'Grundlagen', and was strong emphasised in Wittgenstein's 'Philosophical Investigations'. | |
| From: report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Harold Noonan - Identity §4 | |
| A reaction: For Frege a thing can only have an intrinsic identity if it can participate in an equality relation. For abstract objects (such as directions or numbers) the relation is an equivalence. The general idea is that identical objects must relate in some way. |
| 11100 | Frege's algorithm of identity is the law of putting equals for equals [Frege, by Quine] |
| Full Idea: Frege's algorithm of identity is the law of putting equals for equals. | |
| From: report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Willard Quine - Identity, Ostension, and Hypostasis 4 | |
| A reaction: Quine, and most modern philosophers, seem to accept universal substitutivity as a sufficient condition for identity. But you then get the problem of coextensionality (renate/cordate), which can only be solved by introducing modality. |
| 4893 | Frege was asking how identities could be informative [Frege, by Perry] |
| Full Idea: A problem which Frege called to our attention is: how can identities be informative? | |
| From: report of Gottlob Frege (On Sense and Reference [1892]) by John Perry - Knowledge, Possibility and Consciousness §5.2 | |
| A reaction: E.g. (in Russell's example) how is "Scott is the author of 'Waverley'" more informative than "Scott is Scott"? A simple answer might just be that informative identities also tell you of a thing's properties. "The red ball is the heavy ball". |
| 6056 | Identity is not a relation between objects [Wittgenstein] |
| Full Idea: It is self-evident that identity is not a relation between objects. | |
| From: Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921], 5.5301) | |
| A reaction: Part of Wittgenstein's claim that identity statements are 'pseudo-propositions'. See, in reply, the ideas of McGinn on identity. This was part of the drive that led to the extremes of logical positivism, killing metaphysics for two generations. |
| 17595 | To unite a sequence of ostensions to make one object, a prior concept of identity is needed [Quine] |
| Full Idea: The concept of identity is central in specifying spatio-temporally broad objects by ostension. Without identity, n acts of ostension merely specify up to n objects. ..But when we affirm identity of object between ostensions, they refer to the same object. | |
| From: Willard Quine (Identity, Ostension, and Hypostasis [1950], 1) | |
| A reaction: Quine says that there is an induction involved. On the whole, Quine seems to give a better account of identity than Geach or Wiggins can offer. |
| 18965 | We know what things are by distinguishing them, so identity is part of ontology [Quine] |
| Full Idea: We cannot know what something is without knowing how it is marked off from other things. Identity is thus of a piece with ontology. | |
| From: Willard Quine (Ontological Relativity [1968], p.55) | |
| A reaction: Actually it is failure of identity which seems to raise questions of individuation. If I say 'this apple is [pause] identical to this apple', I don't see how that helps me to individuate apples. |
| 15475 | The concept of 'identity' must allow for some changes in properties or parts [Martin,CB] |
| Full Idea: We must avoid a use of 'identity' that implies that any entity over time must be said to lack continuing identity simply because it has changed properties or has lost, added, or had substituted some parts. | |
| From: C.B. Martin (The Mind in Nature [2008], 04.3) | |
| A reaction: This may the key area where the logical-mathematical type of philosophy comes into contact with the natural-metaphysical type. Imagine Martin's concept of 'identity' in mathematics. π changes to 3.1387... during the calculation! |
| 15486 | Only abstract things can have specific and full identity specifications [Martin,CB] |
| Full Idea: Abstract entities (as nonspatiotemporal) seem to be the only candidates for specific and full identity specifications. | |
| From: C.B. Martin (The Mind in Nature [2008], 05.2 n1) | |
| A reaction: Martin says that only the 'mad logician' seeks such specifications elsewhere. Some people like persons to have perfect identity. God is a popular candidate too. Can objects have perfect 'macroscopic' identity? |
| 18389 | When entities contain entities, or overlap with them, there is 'partial' identity [Armstrong] |
| Full Idea: There is 'partial identity' where one entity contains another with something to spare, or else where entities overlap each other. ...Extensive quantities, such as length and mass, are the particularly plausible cases. | |
| From: David M. Armstrong (Truth and Truthmakers [2004], 08.5) | |
| A reaction: This looks like a very useful concept which deserves wider use. It will help discussions of rivers, statues, intersecting roads etc. |
| 16981 | With the necessity of self-identity plus Leibniz's Law, identity has to be an 'internal' relation [Kripke] |
| Full Idea: It is clear from (x)□(x=x) and Leibniz's Law that identity is an 'internal' relation: (x)(y)(x=y ⊃ □x=y). What pairs (w,y) could be counterexamples? Not pairs of distinct objects, …nor an object and itself. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.03) | |
| A reaction: I take 'internal' to mean that the necessity of identity is intrinsic to the item(s), and not imposed by some other force. |
| 17509 | Some say a 'covering concept' completes identity; others place the concept in the reference [Ayers] |
| Full Idea: Some hold that the 'covering concept' completes the incomplete concept of identity, determining the kind of sameness involved. Others strongly deny the identity itself is incomplete, and locate the covering concept within the necessary act of reference. | |
| From: M.R. Ayers (Individuals without Sortals [1974], Intro) | |
| A reaction: [a bit compressed; Geach is the first view, and Quine the second; Wiggins is somewhere between the two] |
| 4885 | Identity is a very weak relation, which doesn't require interdefinability, or shared properties [Perry] |
| Full Idea: The truth of "a=b" doesn't require much of 'a' and 'b' other than that there is a single thing to which they both refer. They needn't be interdefinable, or have supervenient properties. In this sense, identity is a very weak relation. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §1.2) | |
| A reaction: Interesting. This is seeing the epistemological aspects of identity. Ontologically, identity must invoke Leibniz's Law, and is the ultimately powerful 'relation'. A given student, and the cause of a crop circle, may APPEAR to be quite different. |
| 11843 | Identity over a time and at a time aren't different concepts [Wiggins] |
| Full Idea: People often speak of identity over time and distinguish it from identity at a time. But identity is just identity. | |
| From: David Wiggins (Sameness and Substance Renewed [2001], 2.3) | |
| A reaction: I myself am guilty of such usage, but it doesn't imply a commitment to a multivocal concept. The epistemological issues (of explaining what it is now, and simply reidentifying it later) seem profoundly different. Hume only admits identity over time. |
| 11864 | Hesperus=Hesperus, and Phosphorus=Hesperus, so necessarily Phosphorus=Hesperus [Wiggins] |
| Full Idea: The simple proof (from Ruth Barcan Marcus) is: Hesperus is necessarily Hesperus, so if Phosphorus is Hesperus, then Phosphorus is necessarily Hesperus. | |
| From: David Wiggins (Sameness and Substance Renewed [2001], 4.3) | |
| A reaction: This is the famous idea which she noticed well before Kripke. The point is that the simple logic of the case bestows a necessity on the identity. We shouldn't be confused by the a posteriori and contingent nature of the discovery. |
| 17588 | We should talk of the transitivity of 'identity', and of 'definite identity' [Inwagen] |
| Full Idea: In some contexts, the principle of 'the transitivity of identity' should be called 'the transitivity of definite identity'. | |
| From: Peter van Inwagen (Material Beings [1990], 18) | |
| A reaction: He is making room for a person to retain identity despite having changed. Applause from me. |
| 6058 | Identity propositions are not always tautological, and have a key epistemic role [McGinn] |
| Full Idea: Identity propositions are not always analytic or a priori (as Frege long ago taught us) so there is nothing trivial about such propositions; the claim of redundancy ignores the epistemic role that the concept of identity plays. | |
| From: Colin McGinn (Logical Properties [2000], Ch.1) | |
| A reaction: He is referring to Frege's Morning Star/Evening Star distinction (Idea 4972). Wittgenstein wanted to eliminate our basic metaphysics by relabelling it as analytic or tautological, but his project failed. Long live metaphysics! |
| 11888 | Identities must hold because of other facts, which must be instrinsic [Forbes,G, by Mackie,P] |
| Full Idea: Forbes has two principles of identity, which we can call the No Bare Identities Principle (identities hold in virtue of other facts), and the No Extrinsic Determination Principle (that only intrinsic facts of a thing establish identity). | |
| From: report of Graeme Forbes (The Metaphysics of Modality [1985], 127-8) by Penelope Mackie - How Things Might Have Been 2.7 | |
| A reaction: The job of the philosopher is to prise apart the real identities of things from the way in which we conceive of identities. I take these principles to apply to real identities, not conceptual identities. |
| 15603 | I can only represent individuals as the same if I do not already represent them as the same [Fine,K] |
| Full Idea: I can only represent two individuals as being the same if I do not already represent them as the same. | |
| From: Kit Fine (Semantic Relationism [2007], 3.A) | |
| A reaction: A very nice simple point. If I say 'Hesperus is Hesperus' I am unable to comment on the object, but 'Hesperus is Phosphorus' has a different expressive power. Start from contexts where it is necessary to say that two things are actually one. |
| 10522 | The relations featured in criteria of identity are always equivalence relations [Hale] |
| Full Idea: The relations which are featured in criteria of identity are always equivalence relations. | |
| From: Bob Hale (Abstract Objects [1987], Ch.3.III) | |
| A reaction: This will only apply to strict identity. If I say 'a is almost identical to b', this will obviously not be endlessly transitive (as when we get to k we may have lost the near-identity to a). Are 'two threes' identical to 'three twos'? |
| 8970 | Our notion of identical sets involves identical members, which needs absolute identity [Hawthorne] |
| Full Idea: Our conceptual grip on the notion of a set is founded on the axiom of extensionality: a set x is the same as a set y iff x and y have the same members. But this axiom deploys the notion of absolute identity ('same members'). | |
| From: John Hawthorne (Identity [2003], 3.1) | |
| A reaction: Identity seems to be a primitive, useful and crucial concept, so don't ask what it is. I suspect that numbers can't get off the ground without it (especially, in view of the above, if you define numbers in terms of sets). |