8920
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Equivalence relations are reflexive, symmetric and transitive, and classify similar objects [Lipschutz]
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Full Idea:
A relation R on a non-empty set S is an equivalence relation if it is reflexive (for each member a, aRa), symmetric (if aRb, then bRa), and transitive (aRb and bRc, so aRc). It tries to classify objects that are in some way 'alike'.
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From:
Seymour Lipschutz (Set Theory and related topics (2nd ed) [1998], 3.9)
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A reaction:
So this is an attempt to formalise the common sense notion of seeing that two things have something in common. Presumably a 'way' of being alike is going to be a property or a part
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11842
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If short-lived happenings like car crashes are 'events', why not long-lived events like Dover Cliffs? [Broad]
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Full Idea:
We call a lightning flash or a motor accident an event, but refuse to apply this to the cliffs of Dover. ...But quantitative differences (of time) give no good grounds for calling one bit of history an event, and refusing the name to another bit.
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From:
C.D. Broad (Scientific Thought [1923], p.54), quoted by David Wiggins - Sameness and Substance Renewed 2.3 n13
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A reaction:
Wiggins calls this proposal a 'terrible absurdity', but it seems to me to demand attention. There is a case to be made for a 'process' to be the fundamental category of our ontology, with stable physical objects seen in that light.
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14609
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We could say present and past exist, but not future, so that each event adds to the total history [Broad]
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Full Idea:
One theory accepts the reality of the present and the past, but holds that the future is simply nothing at all. Nothing has happened to the present by becoming past except that fresh slices of existence have been added to the total history of the world.
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From:
C.D. Broad (Scientific Thought [1923], II)
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A reaction:
This is now known as Broad's 'Growing Block' view of time. It is tempting to say that neither past nor future exist, but it seems undeniable that statements about the past can be wholly true, unlike those about the future.
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22933
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We imagine the present as a spotlight, moving across events from past to future [Broad]
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Full Idea:
We imagine presentness moving, like the spot of light from a policeman's bulls eye traversing the fronts of houses in a street. What is illuminated is present, what was illuminated is past, and what is not yet illuminated is the future.
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From:
C.D. Broad (Scientific Thought [1923], II)
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A reaction:
This is the 'moving spotlight' compromise theory, which retains the B-series eternal sequence of ordered events, but adds the A-series privileged present moment. Le Poidevin says Broad represents time twice over.
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