| 223 | If you deny that each thing always stays the same, you destroy the possibility of discussion [Plato] |
| Full Idea: If a person denies that the idea of each thing is always the same, he will utterly destroy the power of carrying on discussion. | |
| From: Plato (Parmenides [c.364 BCE], 135c) |
| 227 | You must always mean the same thing when you utter the same name [Plato] |
| Full Idea: You must always mean the same thing when you utter the same name. | |
| From: Plato (Parmenides [c.364 BCE], 147d) |
| 153 | It takes a person to understand, by using universals, and by using reason to create a unity out of sense-impressions [Plato] |
| Full Idea: It takes a man to understand by the use of universals, and to collect out of the multiplicity of sense-impressions a unity arrived at by a process of reason. | |
| From: Plato (Phaedrus [c.366 BCE], 249b) |
| 2142 | The plurality of beautiful things must belong to a single class, because they have a single particular character [Plato] |
| Full Idea: All the things we refer to as pluralities (e.g. beautiful things) we also count as belonging to a single class by virtue of the fact that they have a single particular character. | |
| From: Plato (The Republic [c.374 BCE], 507b) |
| 649 | The acquisition of scientific knowledge is impossible without universals [Aristotle] |
| Full Idea: The acquisition of scientific knowledge is impossible without universals. | |
| From: Aristotle (Metaphysics [c.324 BCE], 1086b03) |
| 1675 | Separate Forms aren't needed for logic, but universals (one holding of many) are essential [Aristotle] |
| Full Idea: There need be no forms (one item apart from the many) for demonstrations. But there must be universals, where one thing holds of the many. Without universals there are no middle terms, and so no demonstrations. | |
| From: Aristotle (Posterior Analytics [c.327 BCE], 77a05) |
| 21710 | We know a universal in 'yellow differs from blue' or 'yellow resembles blue less than green does' [Russell] |
| Full Idea: We are aware of the universal 'yellow'; this universal is the subject in such judgements as 'yellow differs from blue' or 'yellow resembles blue less than green does'. | |
| From: Bertrand Russell (Knowledge by Acquaintance and Description-1 [1911], 154), quoted by Bernard Linsky - Russell's Metaphysical Logic 2.3 | |
| A reaction: This still seems one of the strongest examples in support of universals. You could hardly be talking about yellow tropes in such instances (even if the world does contain yellow tropes). |
| 4030 | Russell claims that universals are needed to explain a priori knowledge (as their relations) [Russell, by Mellor/Oliver] |
| Full Idea: Russell's positive argument for universals is that they explain how we can have a priori knowledge, which 'deals exclusively with the relations of universals'. | |
| From: report of Bertrand Russell (Problems of Philosophy [1912], Ch. 9) by DH Mellor / A Oliver - Introduction to 'Properties' §3 | |
| A reaction: Unfortunately we can invent the universals, and then delude ourselves that we have a priori knowledge |
| 4427 | Every sentence contains at least one word denoting a universal, so we need universals to know truth [Russell] |
| Full Idea: No sentence can be made up without at least one word which denotes a universal. ..Thus all truths involve universals, and all knowledge of truths involves acquaintance with universals. | |
| From: Bertrand Russell (Problems of Philosophy [1912], Ch. 9) | |
| A reaction: Sounds right, and is a beautifully neat way of showing the connection between metaphysics and life. |
| 3751 | Universals are acceptable if they are needed to make an accepted theory true [Quine, by Jacquette] |
| Full Idea: Abstract entities (universals) are admitted to an ontology by Quine's criterion if they must be supposed to exist (or subsist) in order to make the propositions of an accepted theory true. | |
| From: report of Willard Quine (works [1961]) by Dale Jacquette - Abstract Entity p.3 |
| 4032 | The problem of universals is how many particulars can all be of the same 'type' [Armstrong] |
| Full Idea: The problem of universals is the problem of how numerically different particulars can nevertheless be identical in nature, all be of the same 'type'. | |
| From: David M. Armstrong (Nominalism and Realism [1978], p.41), quoted by DH Mellor / A Oliver - Introduction to 'Properties' §7 | |
| A reaction: A nice statement of the problem. As usual, the question is whether the 'sameness' is a feature of nature, or a product of human thought |
| 8539 | Universals are required to give a satisfactory account of the laws of nature [Armstrong] |
| Full Idea: A reason why I reject trope theory is that universals are required to give a satisfactory account of the laws of nature. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: This is the key thought in Armstrong's defence of universals. Issues about universals may well be decided on such large playing fields. I think he is probably wrong, and I will gradually explain why. Watch this space as the story unfolds... |
| 10729 | Universals explain resemblance and causal power [Armstrong, by Oliver] |
| Full Idea: Armstrong thinks universals play two roles, namely grounding objective resemblances and grounding causal powers. | |
| From: report of David M. Armstrong (A Theory of Universals [1978]) by Alex Oliver - The Metaphysics of Properties 11 | |
| A reaction: Personally I don't think universals explain anything at all. They just add another layer of confusion to a difficult problem. Oliver objects that this seems a priori, contrary to Armstrong's principle in Idea 10728. |
| 17669 | Realist regularity theories of laws need universals, to pick out the same phenomena [Armstrong] |
| Full Idea: A Realistic version of a Regularity theory of laws will have to postulate universals. How else will it be possible to say that the different instances of a certain uniformity are all instances of objectively the same phenomenon? | |
| From: David M. Armstrong (What is a Law of Nature? [1983], 02.4) | |
| A reaction: I disagree. We may (or may not) need properties, but they can be have a range. We just need stable language. We use one word 'red', even when the shade of redness varies. Non-realists presumably refer to sense-data. |
| 9485 | Universals concern how things are, and how they could be [Shoemaker, by Bird] |
| Full Idea: Shoemaker contends that universals concern the way things could be, not merely the way any things actually are. | |
| From: report of Sydney Shoemaker (Causality and Properties [1980]) by Alexander Bird - Nature's Metaphysics 3.2.2 | |
| A reaction: If you want to retain universals within a scientific essentialist view (and I would rather not), then this seems like the only way to go. |
| 8566 | We need universals for causation and laws of nature; the latter give them their identity [Mellor] |
| Full Idea: I take the main reason for believing in contingent universals to be the roles they play in causation and in laws of nature, and those laws are what I take to give those universals their identity. | |
| From: D.H. Mellor (Properties and Predicates [1991], 'Props') | |
| A reaction: He agrees with Armstrong. Sounds a bit circular - laws are built on universals, and universals are identified by laws. It resembles a functionalist account of mental events. I think it is wrong. A different account of laws will be needed... |
| 15436 | Universals are meant to give an account of resemblance [Lewis] |
| Full Idea: Perhaps the main job of a theory of universals is to give an account of resemblance. | |
| From: David Lewis (Against Structural Universals [1986], 'Why believe') | |
| A reaction: This invites the quick reply, popular with some nominalists, of taking resemblance as primitive, and hence beyond explanation. |
| 21961 | Physics aims to discover which universals actually exist [Lewis, by Moore,AW] |
| Full Idea: For Lewis, we can see the purpose of physics as being to discover what universals there actually are. | |
| From: report of David Lewis (New work for a theory of universals [1983]) by A.W. Moore - The Evolution of Modern Metaphysics Intro | |
| A reaction: It seems that Lewis uses the word 'property' to mean predicates, which consist of a multitude of sets, while universals are the properties that naturally exist and cut nature at the joints . Infuriating, because the other way around seems better. |
| 7034 | Universals explain one-over-many relations, and similar qualities, and similar behaviour [Heil] |
| Full Idea: Universals can explain the one-over-many problem, and easily explain similarity relations between objects, and explain the similar behaviour of similar objects. | |
| From: John Heil (From an Ontological Point of View [2003], 13.1) | |
| A reaction: A useful summary. If you accept it, you seem to be faced with a choice between Plato (who has universals existing independently of particulars) and Armstrong (who makes them real, but existing only in particulars). |
| 8293 | Real universals are needed to explain laws of nature [Lowe] |
| Full Idea: I base my case for realism about universals on the need to explain the status of natural laws. | |
| From: E.J. Lowe (The Possibility of Metaphysics [1998], 9.6) | |
| A reaction: I need black magic to explain why my watch has disappeared. The key question, then, would be what we understand by the 'laws of nature'. I am inclined to think that scientific essentialism (qv) can build laws out of natural kinds. Idea 6614. |
| 4450 | The traditional problem of universals centres on the "One over Many", which is the unity of natural classes [Moreland] |
| Full Idea: Historically the problem of universals has mainly been about the "One over Many", which involves giving an account of the unity of natural classes. | |
| From: J.P. Moreland (Universals [2001], Ch.1) | |
| A reaction: This still strikes me as the main problem (rather than issues of language). If universals are not natural, they must be analysed as properties, which break down into causation, which is seen as a human convention. |
| 4449 | Evidence for universals can be found in language, communication, natural laws, classification and ideals [Moreland] |
| Full Idea: Those who believe in universals appeal to the meaningfulness of language, the lawlike nature of causation, the inter-subjectivity of thinking, our ability to classify new entities, gradation, and the need for perfect standards or paradigms. | |
| From: J.P. Moreland (Universals [2001], Ch.1) | |
| A reaction: Of these, language and communication ought to be explicable by convention, but classification and natural laws look to me like the best evidence. |
| 16260 | Existence of universals may just be decided by acceptance, or not, of second-order logic [Maudlin] |
| Full Idea: On one line of thought, the question of whether universals exist seems to reduce to the question of the utility, or necessity, of using second-order rather than first-order logic. | |
| From: Tim Maudlin (The Metaphysics within Physics [2007], 3.1) | |
| A reaction: Second-order logic quantifies over properties, where first-order logic just quantifies over objects. This is an extreme example of doing your metaphysics largely through logic. Not my approach. |
| 7951 | Numerical sameness is explained by theories of identity, but what explains qualitative identity? [Macdonald,C] |
| Full Idea: We can distinguish between numerical identity and qualitative identity. Numerical sameness is explained by a theory of identity, but what explains qualitative sameness? | |
| From: Cynthia Macdonald (Varieties of Things [2005], Ch.6) | |
| A reaction: The distinction is between type and token identity. Tokens are particulars, and types are sets, so her question comes down to the one of what entitles something to be a member of a set? Nothing, if sets are totally conventional, but they aren't. |
| 22134 | Thoughts are general, but the world isn't, so how can we think accurately? [Boulter] |
| Full Idea: Our thoughts are full of generalities, but the world contains no generalities. So how can our thoughts accurately represent the world? This is the problem of universals. | |
| From: Stephen Boulter (Why Medieval Philosophy Matters [2019], 1) | |
| A reaction: I so love it when someone comes up with a really clear explanation of a problem, and this is a beauty from Stephen Boulter. Only a really clear explanation can motivate philosophical issues for non-philosophers. |