Unit quiz: Necessity, time, composition, and the revision of concepts

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Question 1

An essay argues: 'There is a possible world in which you have a sister, so you have a sister in that world, and therefore a sister exists.' A critic says the conclusion does not follow, but a modal realist insists that all possible worlds are as concrete as the actual one. Who is right, and why?The critic is right: 'there is a world where P' quantifies over worlds, and existence at a world is not existence in the actual world; even on concretism, actuality is indexical and the sister is not among the things hereThe modal realist is right, because if all worlds are equally concrete then whatever exists at any world exists without qualification, and actuality is a mere honorific

Question 2

Suzy throws a rock that shatters a bottle; Billy throws too, but his rock arrives a fraction later and would have shattered the bottle had Suzy missed. A lawyer argues that Suzy did not cause the shattering, because had she not thrown the bottle would still have shattered. Assess the argument.It is sound: causation just is counterfactual dependence, so where the effect would have occurred anyway there is no causation, and the later throw is the causeIts second premise is true but its conclusion does not follow as a claim about causation: Suzy's throw is a cause, so counterfactual dependence is not necessary for causation and the theory needs supplementing, for instance by influence or a contrastive formulation

Question 3

McTaggart argues that every event is past, present, and future, that these properties are incompatible, and that the reply that an event is present only now and future later generates a regress. A reader concludes that time is an illusion and that nothing is really earlier than anything else. Where does the argument actually leave the dispute?If sound it shows the A series cannot be fundamental; a B-theorist accepts that verdict and keeps the B series as real, so the conclusion that nothing is earlier than anything else does not followIf sound it shows temporal relations are unreal, since time needs both series and McTaggart has undermined the A series

Question 4

Take a cat. Each of the billions of candidate aggregates of molecules differing from the cat's molecules by a single hair at the boundary seems equally qualified to be the cat, and there is no principled line at which a candidate stops being the cat. A philosopher concludes that there are no cats, only cat-shaped swarms. Assess the conclusion.It follows, because vagueness is always a defect of language, and once language is corrected the swarm is all that remainsIt does not follow: the argument shows that unrestricted composition plus a demand for a unique boundary is unstable, and the alternatives include restricting composition, accepting ontic vagueness, or treating counting as concept-relative

Question 5

In 2006 the International Astronomical Union defined 'planet' so as to exclude Pluto. A textbook author objects that Pluto was a planet before 2006 and that the new definition is therefore false to the facts, while a committee member replies that the definition was adopted because a three-class scheme serves classification better. What is the dispute about?About which concept to use for a purpose, not about a hidden essence; the redefinition is an explication assessed by similarity to prior usage, exactness, and fruitfulness, and its cost is a break in topic continuityAbout an essence that astronomers discovered in 2006, so the textbook author is simply wrong about what 'planet' always meant

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