Combining Texts

All the ideas for 'Leibniz: Guide for the Perplexed', 'fragments/reports' and 'Investigations into Logical Deduction'

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10 ideas

5. Theory of Logic / H. Proof Systems / 4. Natural Deduction
Natural deduction shows the heart of reasoning (and sequent calculus is just a tool) [Gentzen, by Hacking]
     Full Idea: Gentzen thought that his natural deduction gets at the heart of logical reasoning, and used the sequent calculus only as a convenient tool for proving his chief results.
     From: report of Gerhard Gentzen (Investigations into Logical Deduction [1935]) by Ian Hacking - What is Logic? §05
7. Existence / D. Theories of Reality / 4. Anti-realism
For the Cyrenaics experience was not enough to give certainty about reality [Aristippus young, by Plutarch]
     Full Idea: The Cyrenaics, placing all experience within themselves, thought such evidence was insufficient warrant for certainty about reality, and withdrew as in a siege from the world, admitting that objects 'appear', but refusing to pronounce the word 'are'.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Plutarch - 74: Reply to Colotes §1120
     A reaction: This seems to be the most extreme position found in ancient thought. It accompanies their extreme hedonism, based on the reality of experience and lack of interest in anything external. A bit daft, really.
9. Objects / B. Unity of Objects / 2. Substance / d. Substance defined
Substance needs independence, unity, and stability (for individuation); also it is a subject, for predicates [Perkins]
     Full Idea: For individuation, substance needs three properties: independence, to separate it from other things; unity, to call it one thing, rather than an aggregate; and permanence or stability over time. Its other role is as subject for predicates.
     From: Franklin Perkins (Leibniz: Guide for the Perplexed [2007], 3.1)
     A reaction: Perkins is describing the Aristotelian view, which is taken up by Leibniz. 'Substance' is not a controversial idea, if we see that it only means that the world is full of 'things'. It is an unusual philosopher wholly totally denies that.
20. Action / C. Motives for Action / 3. Acting on Reason / b. Intellectualism
Even the foolish may have some virtues [Aristippus young, by Diog. Laertius]
     Full Idea: The Cyrenaics say that some of the virtues may exist even in the foolish.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.8
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / g. Moral responsibility
Actions are influenced by circumstances, so Cyrenaics say felons should be reformed, not hated [Aristippus young, by Diog. Laertius]
     Full Idea: Cyrenaics say errors should be pardoned, because men do not err intentionally but are influenced by circumstances; one should not hate a person, but only teach him better.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.9
     A reaction: A very appealing suggestion, and rather wonderful for its time. There is still implied agreement about what is 'error', and what counts as 'better'.
22. Metaethics / A. Ethics Foundations / 2. Source of Ethics / j. Ethics by convention
Cyrenaics teach that honour, justice and shame are all based on custom and fashion [Aristippus young, by Diog. Laertius]
     Full Idea: The Cyrenaics taught that there was nothing naturally and intrinsically just, or honourable, or disgraceful; but that things were considered so because of law and fashion.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.8
     A reaction: As we would say now, values and virtues are 'cultural constructs'. This obviously contains a lot of truth, but I don't think our opposition of genocide is just 'fashion'.
23. Ethics / A. Egoism / 1. Ethical Egoism
For a Cyrenaic no one is of equal importance to himself [Aristippus young, by Diog. Laertius]
     Full Idea: A Cyrenaic will not consider anyone else of equal importance with himself.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.9
23. Ethics / A. Egoism / 3. Cyrenaic School
No one pleasure is different from or more pleasant than another [Aristippus young, by Diog. Laertius]
     Full Idea: No one pleasure is different from or more pleasant than another.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.8
The Cyrenaics asserted that corporeal pleasures were superior to mental ones [Aristippus young, by Diog. Laertius]
     Full Idea: The Cyrenaics asserted that corporeal pleasures were superior to mental ones.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.8
23. Ethics / C. Virtue Theory / 4. External Goods / d. Friendship
Cyrenaics say wise men are self-sufficient, needing no friends [Aristippus young, by Diog. Laertius]
     Full Idea: Cyrenaics say wise men are sufficient to themselves, and so have no need of friends.
     From: report of Aristippus the younger (fragments/reports [c.335 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.7.13