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Single Idea 18950
[filed under theme 9. Objects / A. Existence of Objects / 2. Abstract Objects / b. Need for abstracta
]
Full Idea
Physics is full of references to such 'non-physical' entities as state-vectors, Hamiltonians, Hilbert space etc.
Gist of Idea
Physics is full of non-physical entities, such as space-vectors
Source
Hilary Putnam (Philosophy of Logic [1971], Ch.2)
Book Ref
Putnam,Hilary: 'Philosophy of Logic' [Routledge 1972], p.14
A Reaction
I take these to be concepts which are 'abstracted' from the physical facts, and so they don't strike me as being much of an ontological problem, or an objection to nominalism (which Putnam takes them to be).
The
14 ideas
from 'Philosophy of Logic'
18949
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The universal syllogism is now expressed as the transitivity of subclasses
[Putnam]
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18951
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For scientific purposes there is a precise concept of 'true-in-L', using set theory
[Putnam]
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18950
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Physics is full of non-physical entities, such as space-vectors
[Putnam]
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18955
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Having a valid form doesn't ensure truth, as it may be meaningless
[Putnam]
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18953
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Modern notation frees us from Aristotle's restriction of only using two class-names in premises
[Putnam]
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18952
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'⊃' ('if...then') is used with the definition 'Px ⊃ Qx' is short for '¬(Px & ¬Qx)'
[Putnam]
|
18954
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Before the late 19th century logic was trivialised by not dealing with relations
[Putnam]
|
18956
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Asserting first-order validity implicitly involves second-order reference to classes
[Putnam]
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18957
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Nominalism only makes sense if it is materialist
[Putnam]
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18958
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In type theory, 'x ∈ y' is well defined only if x and y are of the appropriate type
[Putnam]
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18959
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Sets larger than the continuum should be studied in an 'if-then' spirit
[Putnam]
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18960
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Most predictions are uninteresting, and are only sought in order to confirm a theory
[Putnam]
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18962
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Unfashionably, I think logic has an empirical foundation
[Putnam]
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18961
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We can identify functions with certain sets - or identify sets with certain functions
[Putnam]
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