Combining Texts

Ideas for 'The Rationality of Science', 'Why Medieval Philosophy Matters' and 'The Nature of Necessity'

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4 ideas

10. Modality / A. Necessity / 6. Logical Necessity
22150 Logical possibility needs the concepts of the proposition to be adequate [Boulter]
     Full Idea: One can only be sure that a proposition expresses a genuine logical possibility if one can be sure that one's concepts are adequate to things referred to in the proposition.
     From: Stephen Boulter (Why Medieval Philosophy Matters [2019], 4)
     A reaction: Boulter says this is a logical constraint place on logical possibility by the scholastics which tends to be neglected by modern thinkers, who only worry about whether the proposition implies a contradiction. So we now use thought experiments.
10. Modality / C. Sources of Modality / 1. Sources of Necessity
3867 De re necessity arises from the way the world is [Newton-Smith]
     Full Idea: A necessary truth is 'de re' if its necessity arises from the way the world is.
     From: W.H. Newton-Smith (The Rationality of Science [1981], VII.6)
10. Modality / E. Possible worlds / 1. Possible Worlds / d. Possible worlds actualism
18383 Plantinga says there is just this world, with possibilities expressed in propositions [Plantinga, by Armstrong]
     Full Idea: Plantinga rejects other possible worlds, but adds to our world an uncountable multitude of sets of propositions, each set a way that the world might have been, but is in fact not. (Roughly, for each Lewis world, Plantinga has such a set).
     From: report of Alvin Plantinga (The Nature of Necessity [1974]) by David M. Armstrong - Truth and Truthmakers 07.2
     A reaction: To me it seems as ontologically extravagant to postulate unexpressed propositions as to postulate concrete possible worlds. I think the best line is that there is just the actual world, with the possibilities implied in its dispositions.
10. Modality / E. Possible worlds / 3. Transworld Objects / b. Rigid designation
11891 Possibilities for an individual can only refer to that individual, in some possible world [Plantinga, by Mackie,P]
     Full Idea: Plantinga says for an individual to exist with certain properties in some possible world is simply for it to be true that, had that possible world obtained, that individual would have existed with those properties.
     From: report of Alvin Plantinga (The Nature of Necessity [1974]) by Penelope Mackie - How Things Might Have Been 5.1
     A reaction: This is intended to dissolve the problem of transworld identity, and is certainly a flat rejection of counterparts. I take the point to be that the individual is the key element in defining the possible world, so can't possibly be different.