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8945
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Fuzzy logic has many truth values, ranging in fractions from 0 to 1 [Fisher]
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Full Idea:
In fuzzy logic objects have properties to a greater or lesser degree, and truth values are given as fractions or decimals, ranging from 0 to 1. Not-p is defined as 1-p, and other formula are defined in terms of maxima and minima for sets.
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From:
Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
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A reaction:
The question seems to be whether this is actually logic, or a recasting of probability theory. Susan Haack attacks it. If logic is the study of how truth is preserved as we move between propositions, then 0 and 1 need a special status.
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8951
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Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism [Fisher]
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Full Idea:
For simplicity, we can say that 'classical logic' amounts to the truth of four sentences: 1) either p or not-p; 2) it is not the case that both p and not-p; 3) from p and not-p, infer q; 4) from p or q and not-p, infer q.
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From:
Jennifer Fisher (On the Philosophy of Logic [2008], 12.I)
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A reaction:
[She says there are many ways of specifying classical logic] Intuition suggests that 2 and 4 are rather hard to dispute, while 1 is ignoring some grey areas, and 3 is totally ridiculous. There is, of course, plenty of support for 3!
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8950
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Logic formalizes how we should reason, but it shouldn't determine whether we are realists [Fisher]
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Full Idea:
Even if one is inclined to be a realist about everything, it is hard to see why our logic should be the determiner. Logic is supposed to formalize how we ought to reason, but whether or not we should be realists is a matter of philosophy, not logic.
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From:
Jennifer Fisher (On the Philosophy of Logic [2008], 09.I)
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A reaction:
Nice to hear a logician saying this. I do not see why talk in terms of an object is a commitment to its existence. We can discuss the philosopher's stone, or Arthur's sword, or the Loch Ness monster, or gravitinos, with degrees of commitment.
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14664
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Necessary beings (numbers, properties, sets, propositions, states of affairs, God) exist in all possible worlds [Plantinga]
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Full Idea:
A 'necessary being' is one that exists in every possible world; and only some objects - numbers, properties, pure sets, propositions, states of affairs, God - have this distinction.
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From:
Alvin Plantinga (Actualism and Possible Worlds [1976], 2)
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A reaction:
This a very odd list, though it is fairly orthodox among philosophers trained in modern modal logic. At the very least it looks rather parochial to me.
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8944
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Vagueness can involve components (like baldness), or not (like boredom) [Fisher]
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Full Idea:
Vague terms come in at least two different kinds: those whose constituent parts come in discrete packets (bald, rich, red) and those that don't (beauty, boredom, niceness).
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From:
Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
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A reaction:
The first group seem to be features of the external world, and the second all occur in the mind. Baldness may be vague, but presumably hairs are (on the whole) not. Nature doesn't care whether someone is actually 'bald' or not.
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14666
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Socrates is a contingent being, but his essence is not; without Socrates, his essence is unexemplified [Plantinga]
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Full Idea:
Socrates is a contingent being; his essence, however, is not. Properties, like propositions and possible worlds, are necessary beings. If Socrates had not existed, his essence would have been unexemplified, but not non-existent.
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From:
Alvin Plantinga (Actualism and Possible Worlds [1976], 4)
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A reaction:
This is a distinctive Plantinga view, of which I can make little sense. I take it that Socrates used to have an essence. Being dead, the essence no longer exists, but when we talk about Socrates it is largely this essence to which we refer. OK?
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14662
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Possible worlds clarify possibility, propositions, properties, sets, counterfacts, time, determinism etc. [Plantinga]
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Full Idea:
The idea of possible worlds has delivered insights on logical possibility (de dicto and de re), propositions, properties and sets, counterfactuals, time and temporal relations, causal determinism, the ontological argument, and the problem of evil.
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From:
Alvin Plantinga (Actualism and Possible Worlds [1976], Intro)
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A reaction:
This date (1976) seems to be the high-water mark for enthusiasm about possible worlds. I suppose if we just stick to 'insights' rather than 'answers' then the big claim might still be acceptable. Which problems are created by possible worlds?
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16472
|
Plantinga's actualism is nominal, because he fills actuality with possibilia [Stalnaker on Plantinga]
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Full Idea:
Plantinga's critics worry that the metaphysics is actualist in name only, since it is achieved only by populating the actual world with entities whose nature is explained in terms of merely possible things that would exemplify them if anything did.
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From:
comment on Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
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A reaction:
Plantinga seems a long way from the usual motivation for actualism, which is probably sceptical empiricism, and building a system on what is smack in front of you. Possibilities have to be true, though. That's why you need dispositions in actuality.
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16469
|
Plantinga has domains of sets of essences, variables denoting essences, and predicates as functions [Plantinga, by Stalnaker]
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Full Idea:
The domains in Plantinga's interpretation of Kripke's semantics are sets of essences, and the values of variables are essences. The values of predicates have to be functions from possible worlds to essences.
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From:
report of Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
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A reaction:
I begin to think this is quite nice, as long as one doesn't take the commitment to the essences too seriously. For 'essence' read 'minimal identity'? But I take essences to be more than minimal, so use identities (which Kripke does?).
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16470
|
Plantinga's essences have their own properties - so will have essences, giving a hierarchy [Stalnaker on Plantinga]
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Full Idea:
For Plantinga, essences are entities in their own right and will have properties different from what instantiates them. Hence he will need individual essences of individual essences, distinct from the essences. I see no way to avoid a hierarchy of them.
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From:
comment on Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
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A reaction:
This sounds devastating for Plantinga, but it is a challenge for traditional Aristotelians. Only a logician suffers from a hierarchy, but a scientist might have to live with an essence, which contains a super-essence.
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14663
|
Are propositions and states of affairs two separate things, or only one? I incline to say one [Plantinga]
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Full Idea:
Are there two sorts of thing, propositions and states of affairs, or only one? I am inclined to the former view on the ground that propositions have a property, truth or falsehood, not had by states of affairs.
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From:
Alvin Plantinga (Actualism and Possible Worlds [1976], 1)
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A reaction:
Might a proposition be nothing more than an assertion that a state of affairs obtains? It would then pass his test. The idea that a proposition is a complex of facts in the external world ('Russellian' propositions?) quite baffles me.
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