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10258
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Logical modalities may be acceptable, because they are reducible to satisfaction in models [Shapiro]
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Full Idea:
For many philosophers the logical notions of possibility and necessity are exceptions to a general scepticism, perhaps because they have been reduced to model theory, via set theory. Thus Φ is logically possible if there is a model that satisfies it.
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From:
Stewart Shapiro (Philosophy of Mathematics [1997], 7.1)
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A reaction:
Initially this looks a bit feeble, like an empiricist only believing what they actually see right now, but the modern analytical philosophy project seems to be the extension of logical accounts further and further into what we intuit about modality.
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5047
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The world is physically necessary, as its contrary would imply imperfection or moral absurdity [Leibniz]
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Full Idea:
Although the world is not metaphysically necessary, such that its contrary would imply a contradiction or logical absurdity, it is necessary physically, that is, determined in such a way that its contrary would imply imperfection or moral absurdity.
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From:
Gottfried Leibniz (On the Ultimate Origination of Things [1697], p.139)
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A reaction:
How does Leibniz know things like this? The distinction between 'metaphysical' necessity and 'natural' (what he calls 'physical') necessity is a key idea. But natural necessity is controversial. See 'Essentialism'.
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13084
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How can things be incompatible, if all positive terms seem to be compatible? [Leibniz]
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Full Idea:
It is yet unknown to me what is the reason of the incompossibility of things, or how it is that different essences can be opposed to each other, seeing that all purely positive terms seem to be compatible.
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From:
Gottfried Leibniz (works [1690], G VII:194), quoted by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 3.4.4
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A reaction:
Since 'heavy' seems straightforwardly opposed to 'light', we would have to ask what he means by 'positive'. The suspicion is that all things are compossible by definition, so it is not surprising that impossibilities are a bit puzzling.
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12732
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Some necessary truths are brute, and others derive from final causes [Leibniz]
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Full Idea:
There is a difference between truths whose necessity is brute and geometric and those truths which have their source in fitness and final causes.
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From:
Gottfried Leibniz (Letters to Remond de Montmort [1715], 1715.06.22/G III 645), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 6
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A reaction:
The second one is a necessity deriving from God's wisdom. Strictly it could have been otherwise, unlike 'geometrical' necessity, which is utterly fixed.
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17079
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Proofs of necessity come from the understanding, where they have their source [Leibniz]
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Full Idea:
The fundamental proof of necessary truths comes from the understanding alone, and other truths come from experience or from observations of the senses. Our mind is capable of knowing truths of both sorts, but it is the source of the former.
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From:
Gottfried Leibniz (New Essays on Human Understanding [1704], 1.01)
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A reaction:
Interesting because it not only spells out that necessary truths are known a priori, but also explicitly says that the understanding is the 'source' of the truths, or at least the source of their proofs. He also says possibilities derive from essences.
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12736
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If we understand God and his choices, we have a priori knowledge of contingent truths [Leibniz, by Garber]
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Full Idea:
Insofar as we have some insight into how God chooses, we can know a priori the laws of nature that God chooses for this best of all possible worlds. In this way, it is possible to have genuine a priori knowledge of contingent truths.
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From:
report of Gottfried Leibniz (Conspectus libelli (book outline) [1678], A6.4.1998-9) by Daniel Garber - Leibniz:Body,Substance,Monad 6
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A reaction:
I think it would be doubtful whether our knowledge of God's choosings would count as a priori. How do we discover them? Ah! We derive God from the ontological argument, and his choosings from the divine perfection implied thereby.
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15883
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Leibniz narrows down God's options to one, by non-contradiction, sufficient reason, indiscernibles, compossibility [Leibniz, by Harré]
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Full Idea:
Leibniz sets up increasingly stringent conditions possible worlds must meet. The weakest is non-contradiction, for truths of reason; then sufficient reason, for rational worlds; then identity of indiscernibles, for duplicates; then compossibility.
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From:
report of Gottfried Leibniz (works [1690]) by Rom Harré - Laws of Nature 4
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A reaction:
[my summary of a very nice two pages by Harré] God is the source of the principles which do the narrowing down.
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7837
|
Leibniz proposed possible worlds, because they might be evil, where God would not create evil things [Leibniz, by Stewart,M]
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Full Idea:
In his early writings the principle of sufficient reason made it difficult for Leibniz to conceive of possible things;...raising this to possible worlds means God does not choose things that are evil, but chooses a world which must have evil in it.
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From:
report of Gottfried Leibniz (works [1690]) by Matthew Stewart - The Courtier and the Heretic Ch.14
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A reaction:
Where we think of possible worlds as explanations for conditional and counterfactual truths (I take it), Leibniz developed the original idea as part of his huge effort to achieve a consistent theodicy.
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12904
|
If varieties of myself can be conceived of as distinct from me, then they are not me [Leibniz]
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Full Idea:
I can as little conceive of different varieties of myself as of a circle whose diameters are not all of equal length. These variations would all be distinct one from another, and thus one of these varieties of myself would necessarily not be me.
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From:
Gottfried Leibniz (Letters to Antoine Arnauld [1686], 1686.05.13)
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A reaction:
This seems to be, at the very least, a rejection of any idea that I could have a 'counterpart'. It is unclear, though, where he would place a version of himself who learned a new language, or who might have had, but didn't have, a haircut.
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11981
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If someone's life went differently, then that would be another individual [Leibniz]
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Full Idea:
If the life of some person, or something went differently than it does, nothing would stop us from saying that it would be another person, or another possible universe which God had chosen. So truly it would be another individual.
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From:
Gottfried Leibniz (Letters to Antoine Arnauld [1686], 1686.07.14)
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A reaction:
Plantinga quotes this as an example of 'worldbound individuals'. This sort of remark leads to people saying that Leibniz believes all properties are essential, since they assume that his notion of essence is bound up with identity. But is it?
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13080
|
Leibniz has a counterpart view of de re counterfactuals [Leibniz, by Cover/O'Leary-Hawthorne]
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Full Idea:
When Leibniz has the grounds of de re counterfactuals in mind, a counterpart picture, we have argued, is at work.
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From:
report of Gottfried Leibniz (works [1690]) by Cover,J/O'Leary-Hawthorne,J - Substance and Individuation in Leibniz 3.2.2
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A reaction:
If Leibniz were a 'superessentialist', then individuals would be totally worldbound (because their relations would be essential). Cover/Hawthorne argue that he is just a 'strong' essentialist, allowing possible counterparts. Quite persuasive.
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5039
|
If non-existents are possible, their existence would replace what now exists, which cannot therefore be necessary [Leibniz]
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Full Idea:
If certain possibles never exist, then existing things are not always necessary; otherwise it would be impossible for other things to exist instead of them, and so all things that never exist would be impossible.
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From:
Gottfried Leibniz (On Freedom [1689], p.106)
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A reaction:
A neat argument, though it is not self-evident that when possibles came into existence they would have to replace what is already there. Can't something be possible, but only in another world, because this one is already booked?
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