|Necessity, philosophy: different kinds of necessity are distinguished, differing in their strength. For example, physical, logical or metaphysical necessity. See also necessity de dicto, necessity de re.|
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Logical Necessity/Armstrong: strongest - physical necessity: weaker, because contingent! - Even weaker: all-quantification (mere uniformity) - Important Argument: it is impossible to infer from law to all-quantification - Law: physical need.
Necessity/UniversalsArm: now we can clarify the concept of N between U - we translate "N(F,G)" (the assertion of a state, which is at the same time a relationship) as follows: the F-ness of something makes the G-ness of the same thing necessary by virtue of the universals F and G - that is not simply: all-quantification: for all x, x". F-ness makes it necessary that x is G - that would regularity theory - N/Armstrong: rather between types than between tokens - the F-ness of something, not a"s F-ness.
Necessity/Possible World/Poss.W./Armstrong: possible worlds do not need "possibilia" themselves - Necessity: does not have to be equal in all possible worlds! - In some possible worlds the necessity might not apply - a law of nature can have different status in different possible worlds - Notation: "square" N": necessity in all possible worlds - (strong necessity) - III 166 weak necessity: not all possible worlds - notation:"necessary (square) (Sok) exists > Sok is human)" (operator before the entire conditional (range) - III 164 ArmstrongVsStrong N: requires U to be necessary - but Universals are contingent - III 165 VsStrong Necessity in possible worlds where there are no Fs and Gs it is obliged to uninstantiated universals.
Necessity/Place: (conceptualist): only de dicto! - Only type of de re: causal necessity: but contrast here is not contingency, but independence - whether causal need is present, is observed a posteriori (therefore contingent) - contingent: i.e. the dependence was causal or it was not.
Necessity/de dicto: (a priori): can something be denied without contradiction? (Linguistic question) - according to this criterion: token identity: typically contingent - type identity: typically necessary - Conceptualism/Place: contingent hypotheses of type-identity become a necessary truth, when the conventional criteria of attribution of universals change.
Necessity/Armstrong: stems only from identity! - Logical possibility: is not possible between separate entities (E.g. cause/effect)! - (Controversial).
Necessity/Contingency/Quine/Martin: puts both on the same level (like many precursors) early: seemed to tip towards the side of contingency, late: according to the necessity: Figures for physics, or principle of identity of empirically isomorphic theories.
AR II = Disp
D. M. Armstrong
Dispositions, Tim Crane, London New York 1996
What is a Law of Nature? Cambridge 1983