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14. Science / C. Induction / 5. Paradoxes of Induction / a. Grue problem

[problem of a predicate which changes over time]

20 ideas
Goodman showed that every sound inductive argument has an unsound one of the same form [Goodman, by Putnam]
     Full Idea: Goodman has shown that no purely formal criterion can distinguish arguments that are intuitively sound inductive arguments for unsound ones: for every sound one there is an unsound one of the same form. The predicates in the argument make the difference.
     From: report of Nelson Goodman (Fact, Fiction and Forecast (4th ed) [1954]) by Hilary Putnam - Why there isn't a ready-made world 'Causation'
     A reaction: This is to swallow grue whole. I think a bit more chewing is called for. By this date Putnam strikes me as a crazy relativist who has lost his grip on the world. Note the word 'formal' - but Putnam seems to think the argument is important.
Goodman argued that the confirmation relation can never be formalised [Goodman, by Horsten/Pettigrew]
     Full Idea: Goodman constructed arguments that purported to show that a satisfactory syntactic analysis of the confirmation relation can never be found. In response, philosophers of science tried to model it in probabilistic terms.
     From: report of Nelson Goodman (Fact, Fiction and Forecast (4th ed) [1954]) by Horsten,L/Pettigrew,R - Mathematical Methods in Philosophy 4
     A reaction: I take this idea to say that Bayesianism was developed in response to the grue problem. This is an interesting light on 'grue', which never bothered me much. The point is it scuppered formal attempts to model induction.
Grue and green won't be in the same world, as that would block induction entirely [Goodman]
     Full Idea: Grue cannot be a relevant kind for induction in the same world as green, for that would preclude some of the decisions, right or wrong, that constitute inductive inference.
     From: Nelson Goodman (Ways of Worldmaking [1978], 1.4b)
     A reaction: This may make 'grue' less mad than I thought it was. I always assume we are slicing the world as 'green, blue and grue'. I still say 'green' is a basic predicate of experience, but 'grue' is amenable to analysis.
Grue is a puzzle because the notions of similarity and kind are dubious in science [Quine]
     Full Idea: What makes Goodman's example a puzzle is the dubious scientific standing of a general notion of similarity, or of kind.
     From: Willard Quine (Natural Kinds [1969], p.116)
     A reaction: Illuminating. It might be best expressed as revealing a problem with sortal terms, as employed by Geach, or by Wiggins. Grue is a bit silly, but sortals are subject to convention and culture. 'Natural' properties seem needed.
Unlike 'green', the 'grue' predicate involves a time and a change [Armstrong]
     Full Idea: The predicate 'grue' involves essential reference to a particular time, which 'green' does not. Also on the 'grue' hypothesis a change occurs in emeralds in a way that change does not occur on the 'green' hypothesis.
     From: David M. Armstrong (What is a Law of Nature? [1983], 04.5)
     A reaction: I'm inclined to think that comparing 'grue' with 'green' is a category mistake. 'Grue' is a behaviour. Armstrong says this is no objection, because Goodman's argument is purely formal.
Science suggests that the predicate 'grue' is not a genuine single universal [Armstrong]
     Full Idea: It is plausible to say, on the basis of total science, that 'grue' is a predicate to which no genuine, that is, unitary, universal corresponds.
     From: David M. Armstrong (What is a Law of Nature? [1983], 06.7)
Emeralds are naturally green, and only an external force could turn them blue [Ellis]
     Full Idea: Emeralds cannot all turn blue in 2050 (as Nelson Goodman envisaged), because to do so they would have to have an extrinsically variable nature.
     From: Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.7)
     A reaction: I was never very impressed by the 'grue' problem, probably for this reason, but also because Goodman probably thought predicates and properties are the same thing, which they aren't (Idea 5457).
'Grue' introduces a new causal hypothesis - that emeralds can change colour [Harré]
     Full Idea: In introducing the predicate 'grue' we also introduce an additional causal hypothesis into our chemistry and physics; namely, that when observed grue emeralds change from blue to green.
     From: Rom Harré (Laws of Nature [1993], 5)
     A reaction: [The 'when observered' is a Harré addition] I hate 'grue'. Only people who think our predicates have very little to do with reality are impressed by it. Grue is a behaviour, not a colour.
The grue problem shows that natural kinds are central to science [Harré]
     Full Idea: The grue problem illustrates the enormous importance that the concept of a natural-kind plays in real science.
     From: Rom Harré (Laws of Nature [1993], 5)
     A reaction: The point is that we took emeralds to be a natural kind, but 'grue' proposes that they aren't, since stability is the hallmark of a natural kind.
'Grue' only has causal features because of its relation to green [Shoemaker]
     Full Idea: Perhaps 'grue' has causal features, but only derivatively, in virtue of its relation to green.
     From: Sydney Shoemaker (Causal and Metaphysical Necessity [1998], III)
     A reaction: I take grue to be a behaviour, and not a property at all. The problem only arises because the notion of a 'property' became too lax. Presumably Shoemaker should also mention blue in his account.
Grueness is not, unlike green and blue, associated with causal potential [Shoemaker]
     Full Idea: Grueness, as defined by Goodman, is not associated in the way greenness and blueness are with causal potentialities.
     From: Sydney Shoemaker (Causality and Properties [1980], §06)
     A reaction: Expressed rather more simply in Idea 7296. 'Grue' is a characteristic production of a predicate nominalist (i.e. Goodman), and that theory is just wrong. The account of properties must mesh with the account of induction.
To just expect unexamined emeralds to be grue would be totally unreasonable [Lewis]
     Full Idea: Some beliefs are just unreasonable in a strong sense. Think of the man who, for no special reason, expects unexamined emeralds to be grue.
     From: David Lewis (On the Plurality of Worlds [1986], 1.4)
     A reaction: This is a nice converse way of seeing the point that 'grue' is such an totally artificial predicate. I still say that the most illuminating point is that grue is not a colour, so seeing a grue thing is no confirmation at all.
Observing lots of green x can confirm 'all x are green' or 'all x are grue', where 'grue' is arbitrary [Mautner, by PG]
     Full Idea: Observing green emeralds can confirm 'all emeralds are green' or 'all emeralds are grue', where 'grue' is an arbitrary predicate meaning 'green until t and then blue'. Thus predictions are arbitrary, depending on how the property is described.
     From: report of Thomas Mautner (Penguin Dictionary of Philosophy [1996], p.225) by PG - Db (ideas)
     A reaction: This increasingly strikes me as the sort of sceptical nonsense that is concocted by philosophers who are enthralled to language instead of reality. It does draw attention to an expectation of stability in induction, both in language and in nature.
Predictions are bound to be arbitrary if they depend on the language used [Bernecker/Dretske]
     Full Idea: The new riddle of induction ('grue') seems to demonstrate that sound inductive inferences are arbitrary because they depend on the actual language people use to formulate predictions.
     From: Bernecker / Dretske (Knowledge:Readings in Cont.Epist [2000], Pt.V Int)
Problem predicates in induction don't reflect the structure of nature [Sider]
     Full Idea: 'Is nonblack', 'is a nonraven', and 'grue' fail to carve at the joints.
     From: Theodore Sider (Writing the Book of the World [2011], 03.3)
     A reaction: A lot more than this needs to said, but this remark encapsulates why I find most of these paradoxes of induction uninteresting. They are all the creations of logicians, rather than of scientists.
Two applications of 'grue' do not guarantee a similarity between two things [Sider]
     Full Idea: The applicability of 'grue' to each of a pair of particulars does not guarantee the similarity of those particulars.
     From: Theodore Sider (Writing the Book of the World [2011], 06.2)
     A reaction: Grue is not a colour but a behaviour. If two things are 'mercurial' or 'erratic', will that ensure a similarity at any given moment?
Any conclusion can be drawn from an induction, if we use grue-like predicates [Bird]
     Full Idea: It looks as if any claim about the future can be made to be a conclusion of an inductive argument from any premises about the past, as long as we use a strange enough grue-like predicate.
     From: Alexander Bird (Philosophy of Science [1998], Intro)
     A reaction: So don't use strange grue-like predicates. If all our predicates randomly changed their reference each day, we would be unable to talk to one another at all. Emeralds don't change their colour-properties, so why change the predicates that refer to them?
Several months of observing beech trees supports the deciduous and evergreen hypotheses [Bird]
     Full Idea: If someone were to observe beech trees every day over one summer they would have evidence that seems to support both the hypothesis that beech trees are deciduous and the hypothesis that they are evergreens.
     From: Alexander Bird (Philosophy of Science [1998], Intro)
     A reaction: Bird offers this to anyone who (like me) is tempted to dismiss the 'grue' problem as ridiculous. Obviously he is right; 'deciduous' works like 'grue'. But we invented the predicate 'deciduous' to match an observed property.
We normally learn natural kinds from laws, but Goodman shows laws require prior natural kinds [Bird]
     Full Idea: We know what natural kinds there are by seeing which properties appear in the laws of nature. But one lesson of Goodman's problem is that we cannot identify the laws of nature without some prior identification of natural kinds.
     From: Alexander Bird (Philosophy of Science [1998], Ch.7)
     A reaction: For Goodman's problem, see Idea 4783. The essentialist view is that the natural kinds come first, and the so-called 'laws' are just regularities in events that arise from the interaction of stable natural kinds. (Keep predicates and properties separate).
'Grue' is not a colour [Milsted]
     Full Idea: 'Grue' is not a colour.
     From: Tom Milsted (talk [2006]), quoted by PG - Db (ideas)
     A reaction: This simple observation strikes me as rather crucial in assessing Goodman's paradox. Blue is a colour, but grue is some sort of behaviour. Blue is a secondary quality, but grue seems to be a primary quality.