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All the ideas for 'On the Philosophy of Logic', 'The Nature of Rationality' and 'Phaedrus'

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40 ideas

1. Philosophy / D. Nature of Philosophy / 1. Philosophy
Can we understand an individual soul without knowing the soul in general? [Plato]
     Full Idea: Do you think it possible to form an adequate conception of the nature of an individual soul without considering the nature of soul in general?
     From: Plato (Phaedrus [c.366 BCE], 270c)
     A reaction: Do animals understand anything (as opposed to simply being aware of things)?
1. Philosophy / D. Nature of Philosophy / 2. Invocation to Philosophy
The highest ability in man is the ability to discuss unity and plurality in the nature of things [Plato]
     Full Idea: When I believe that I have found in anyone the ability to discuss unity and plurality as they exist in the nature of things, I follow his footsteps as if he was a god.
     From: Plato (Phaedrus [c.366 BCE], 266b)
     A reaction: This sounds like the problem of identity, which is at the heart of modern metaphysics.
1. Philosophy / F. Analytic Philosophy / 2. Analysis by Division
A speaker should be able to divide a subject, right down to the limits of divisibility [Plato]
     Full Idea: A speaker must be able to define a subject generically, and then to divide it into its various specific kinds until he reaches the limits of divisibility.
     From: Plato (Phaedrus [c.366 BCE], 277b)
2. Reason / A. Nature of Reason / 1. On Reason
We reach 'reflective equilibrium' when intuitions and theory completely align [Fisher]
     Full Idea: A state of 'reflective equilibrium' is when our theory and our intuitions become completely aligned
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.IV)
     A reaction: [Rawls made this concept famous] This is a helpful concept in trying to spell out the ideal which is the dream of believers in 'pure reason' - that there is a goal in which everything comes right. The problem is when people have different intuitions!
3. Truth / A. Truth Problems / 3. Value of Truth
I do not care if my trivial beliefs are false, and I have no interest in many truths [Nozick]
     Full Idea: I find that I do not mind at all the thought that I have some false beliefs (of US state capitals), and there are many truths I do not care to know at all (total grains of sand on the beach).
     From: Robert Nozick (The Nature of Rationality [1993], p.67)
     A reaction: A useful corrective to anyone who blindly asserts that truth is the supreme human value. I would still be annoyed if someone taught me lies about these two types of truth.
3. Truth / E. Pragmatic Truth / 1. Pragmatic Truth
Maybe James was depicting the value of truth, and not its nature [Nozick]
     Full Idea: We might see William James's pragmatic view that truth is what works as depicting the value of truth, and not its nature.
     From: Robert Nozick (The Nature of Rationality [1993], p.68)
     A reaction: James didn't think that he was doing this. He firmly says that this IS truth, not just the advantages of truth. Another view is that pragmatists are giving a test for truth.
4. Formal Logic / E. Nonclassical Logics / 3. Many-Valued Logic
Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher]
     Full Idea: In three-valued logic (L3), neither the law of excluded middle (p or not-p), nor the law of non-contradiction (not(p and not-p)) will be tautologies. If p has the value 'indeterminate' then so will not-p.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.I)
     A reaction: I quite accept that the world is full of indeterminate propositions, and that excluded middle and non-contradiction can sometimes be uncertain, but I am reluctant to accept that what is being offered here should be called 'logic'.
4. Formal Logic / E. Nonclassical Logics / 4. Fuzzy Logic
Fuzzy logic has many truth values, ranging in fractions from 0 to 1 [Fisher]
     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.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
     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.
5. Theory of Logic / A. Overview of Logic / 6. Classical Logic
Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism [Fisher]
     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.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 12.I)
     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!
5. Theory of Logic / C. Ontology of Logic / 2. Platonism in Logic
Logic formalizes how we should reason, but it shouldn't determine whether we are realists [Fisher]
     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.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 09.I)
     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.
7. Existence / D. Theories of Reality / 2. Realism
Reasoning needs to cut nature accurately at the joints [Plato]
     Full Idea: In our reasoning we need a clear view of the ability to divide a genus into species, observing the natural joints, not mangling any of the parts, like an unskilful butcher.
     From: Plato (Phaedrus [c.366 BCE], 265d)
     A reaction: In modern times this Platonic idea has become the standard metaphor for realism. I endorse it. I think nature has joints, and we should hunt for them. There are natural sets. The joints may exist in abstract concepts, as well as in objects.
7. Existence / D. Theories of Reality / 10. Vagueness / g. Degrees of vagueness
We could make our intuitions about heaps precise with a million-valued logic [Fisher]
     Full Idea: We could construct a 1,000,000-valued logic that would allow our intuitions concerning a heap to vary exactly with the amount of sand in the heap.
     From: Jennifer Fisher (On the Philosophy of Logic [2008])
     A reaction: Presumably only an infinite number of grains of sand would then produce a true heap, and even one grain would count as a bit of a heap, which must both be wrong, so I can't see this helping much.
7. Existence / E. Categories / 2. Categorisation
I revere anyone who can discern a single thing that encompasses many things [Plato]
     Full Idea: If I believe that someone is capable of discerning a single thing that is also by nature capable of encompassing many, I follow 'straight behind, in his footsteps, as if he were a god'.
     From: Plato (Phaedrus [c.366 BCE], 266b)
     A reaction: [Plato quote Odyssey 2.406] This is the sort of simple but profound general observation which only the early philosophers bothered to make, and no one comments on now. Encompassing many under one is the very essence of thinking.
8. Modes of Existence / D. Universals / 2. Need for Universals
It takes a person to understand, by using universals, and by using reason to create a unity out of sense-impressions [Plato]
     Full Idea: It takes a man to understand by the use of universals, and to collect out of the multiplicity of sense-impressions a unity arrived at by a process of reason.
     From: Plato (Phaedrus [c.366 BCE], 249b)
8. Modes of Existence / D. Universals / 6. Platonic Forms / a. Platonic Forms
We would have an overpowering love of knowledge if we had a pure idea of it - as with the other Forms [Plato]
     Full Idea: What overpowering love knowledge would inspire if it could bring a clear image of itself before our sight, and the same may be said of the other forms.
     From: Plato (Phaedrus [c.366 BCE], 250d)
     A reaction: the motivation in Plato's theory
9. Objects / B. Unity of Objects / 3. Unity Problems / e. Vague objects
Vagueness can involve components (like baldness), or not (like boredom) [Fisher]
     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).
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 07.II)
     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.
10. Modality / B. Possibility / 1. Possibility
We can't explain 'possibility' in terms of 'possible' worlds [Fisher]
     Full Idea: Explaining 'it is possible that p' by saying p is true in at least one possible world doesn't get me very far. If I don't understand what possibility is, then appealing to possible worlds is not going to do me much good.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 06.III)
     A reaction: This seems so blatant that I assume friends of possible worlds will have addressed the problem. Note that you will also need to understand 'possible' to define necessity as 'true in all possible worlds'. Necessarily-p is not-possibly-not-p.
10. Modality / B. Possibility / 8. Conditionals / c. Truth-function conditionals
If all truths are implied by a falsehood, then not-p might imply both q and not-q [Fisher]
     Full Idea: If all truths are implied by a falsehood, then 'if there are no trees in the park then there is no shade' and 'if there are no trees in the park there is plenty of shade' both come out as true. Intuitively, though, the second one is false.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.I)
     A reaction: The rule that a falsehood implies all truths must be the weakest idea in classical logic, if it actually implies a contradiction. This means we must take an interest in relevance logics.
10. Modality / B. Possibility / 8. Conditionals / d. Non-truthfunction conditionals
In relevance logic, conditionals help information to flow from antecedent to consequent [Fisher]
     Full Idea: A good account of relevance logic suggests that a conditional will be true when the flow of information is such that a conditional is the device that helps information to flow from the antecedent to the consequent.
     From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.III)
     A reaction: Hm. 'If you are going out, you'll need an umbrella'. This passes on information about 'out', but also brings in new information. 'If you are going out, I'm leaving you'. What flows is an interpretation of the antecedent. Tricky.
12. Knowledge Sources / C. Rationalism / 1. Rationalism
True knowledge is of the reality behind sense experience [Plato]
     Full Idea: True knowledge is concerned with the abode of true reality, without colour or shape, intangible but utterly real, apprehensible only to the intellect.
     From: Plato (Phaedrus [c.366 BCE], 247c)
14. Science / A. Basis of Science / 5. Anomalies
If the apparent facts strongly conflict with probability, it is in everyone's interests to suppress the facts [Plato]
     Full Idea: There are some occasions when both prosecution and defence should positively suppress the facts in favour of probability, if the facts are improbable.
     From: Plato (Phaedrus [c.366 BCE], 272e)
15. Nature of Minds / A. Nature of Mind / 2. Psuche
The soul is self-motion [Plato]
     Full Idea: Self-motion is of the very nature of the soul.
     From: Plato (Phaedrus [c.366 BCE], 245e)
     A reaction: This culminates a length discussion of the soul. He gives an implausible argument that the soul is immortal, because it could never cease its self-motion. Why are we so unimpressed by motion, when the Greeks were amazed by it?
18. Thought / A. Modes of Thought / 3. Emotions / g. Controlling emotions
Plato saw emotions and appetites as wild horses, in need of taming [Plato, by Goldie]
     Full Idea: Plato had a conception of the emotions and our bodily appetites as being like wild horses, to be harnassed and controlled by reason.
     From: report of Plato (Phaedrus [c.366 BCE]) by Peter Goldie - The Emotions 4 'Education'
     A reaction: This seems to make Plato the patriarch of puritanism. See Symposium, as well as Phaedrus. But bringing up children can often seem like taming wild beasts.
18. Thought / A. Modes of Thought / 5. Rationality / a. Rationality
In the instrumental view of rationality it only concerns means, and not ends [Nozick]
     Full Idea: On the instrumental conception of rationality, it consists in the effective and efficient achievement of goals, ends, and desires. About the goals themselves it has little to say.
     From: Robert Nozick (The Nature of Rationality [1993], p.64)
     A reaction: [He quotes Russell 1954 p.viii as expressing this view] A long way from Greek logos, which obviously concerns the rational selection of right ends (for which, presumably, reasons can be given). In practice our ends may never be rational, of course.
Is it rational to believe a truth which leads to permanent misery? [Nozick]
     Full Idea: If a mother is presented with convincing evidence that her son has committed a grave crime, but were she to believe it that would make her life thereafter miserable, is it rational for her to believe her son is guilty?
     From: Robert Nozick (The Nature of Rationality [1993], p.69)
     A reaction: I assume there is a conflict of rationalities, because there are conflicting ends. Presumably most mothers love the truth, but most of us also aim for happy lives. It is perfectly rational to avoid discovering a horrible family truth.
Rationality needs some self-consciousness, to also evaluate how we acquired our reasons [Nozick]
     Full Idea: Rationality involves some degree of self-consciousness. Not only reasons are evaluated, but also the processes by which information arrives, is stored, and recalled.
     From: Robert Nozick (The Nature of Rationality [1993], p.74)
     A reaction: I defend the idea that animals have a degree of rationality, because they can make sensible judgements, but I cannot deny this idea. Rationality comes in degrees, and second-level thought is a huge leap forward in degree.
Rationality is normally said to concern either giving reasons, or reliability [Nozick]
     Full Idea: The two themes permeating the philosophical literature are that rationality is a matter of reasons, or that rationality is a matter of reliability.
     From: Robert Nozick (The Nature of Rationality [1993], p.64)
     A reaction: Since a clock can be reliable, I would have thought it concerns reasons. Or an unthinking person could reliably recite truths from memory. There is also the instrumental view of rationality.
19. Language / F. Communication / 1. Rhetoric
An excellent speech seems to imply a knowledge of the truth in the mind of the speaker [Plato]
     Full Idea: If a speech is to be classed as excellent, does that not presuppose knowledge of the truth about the subject of the speech in the mind of the speaker.
     From: Plato (Phaedrus [c.366 BCE], 259e)
     A reaction: I like the thought that Plato's main interest was rhetoric, but with the view that the only good rhetoric is truth-speaking. It would be hard to admire a speech if you disagreed with it.
Only a good philosopher can be a good speaker [Plato]
     Full Idea: Unless a man becomes an adequate philosopher he will never be an adequate speaker on any subject.
     From: Plato (Phaedrus [c.366 BCE], 261a)
     A reaction: Depends. Hitler showed little sign of clear philosophical thinking, but the addition of lights and uniforms seemed to sweep reasonably intelligent people along with him.
'Phaedrus' pioneers the notion of philosophical rhetoric [Lawson-Tancred on Plato]
     Full Idea: The purpose of the 'Phaedrus' is to pioneer the notion of philosophical rhetoric.
     From: comment on Plato (Phaedrus [c.366 BCE], Ch.10) by Hugh Lawson-Tancred - Plato's Republic and Greek Enlightenment
     A reaction: This is a wonderfully challenging view of what Plato was up to. One might connect it with Rorty's claim that philosophy should move away from epistemology and analysis, towards hermeneutics, which sounds to me like rhetoric. 'Phaedrus' is beautiful.
21. Aesthetics / A. Aesthetic Experience / 4. Beauty
Beauty is the clearest and most lovely of the Forms [Plato]
     Full Idea: Only beauty has the privilege of being the most clearly discerned and the most lovely of the forms.
     From: Plato (Phaedrus [c.366 BCE], 250e)
     A reaction: the motivation in Plato's theory
22. Metaethics / A. Ethics Foundations / 2. Source of Ethics / e. Human nature
The two ruling human principles are the natural desire for pleasure, and an acquired love of virtue [Plato]
     Full Idea: In each one of us there are two ruling and impelling principles: a desire for pleasure, which is innate, and an acquired conviction which causes us to aim at excellence.
     From: Plato (Phaedrus [c.366 BCE], 237d)
     A reaction: This division is too neat and simple. An obsession with pleasure I would take to be acquired. If you set out to do something, I think there is an innate desire to do it well.
22. Metaethics / C. The Good / 3. Pleasure / c. Value of pleasure
Most pleasure is release from pain, and is therefore not worthwhile [Plato]
     Full Idea: Life is not worth living for pleasures whose enjoyment entirely depends on previous sensation of pain, like almost all physical pleasures.
     From: Plato (Phaedrus [c.366 BCE], 258e)
     A reaction: Eating exotic food which is hard to obtain? (Pay someone to obtain it). Rock climbing. Training for sport.
23. Ethics / C. Virtue Theory / 2. Elements of Virtue Theory / c. Motivation for virtue
Reason impels us towards excellence, which teaches us self-control [Plato]
     Full Idea: The conviction which impels us towards excellence is rational, and the power by which it masters us we call self-control.
     From: Plato (Phaedrus [c.366 BCE], 237e)
23. Ethics / C. Virtue Theory / 4. External Goods / d. Friendship
Bad people are never really friends with one another [Plato]
     Full Idea: It is not ordained that bad men should be friends with one another.
     From: Plato (Phaedrus [c.366 BCE], 255b)
27. Natural Reality / E. Cosmology / 3. The Beginning
If the prime origin is destroyed, it will not come into being again out of anything [Plato]
     Full Idea: If the prime origin is destroyed, it will not come into being again out of anything.
     From: Plato (Phaedrus [c.366 BCE], 245d)
     A reaction: This is the essence of Aquinas's Third Way of proving God's existence.
28. God / A. Divine Nature / 3. Divine Perfections
The mind of God is fully satisfied and happy with a vision of reality and truth [Plato]
     Full Idea: The mind of a god, sustained by pure intelligence and knowledge, is satisfied with the vision of reality, and nourished and made happy by the vision of truth.
     From: Plato (Phaedrus [c.366 BCE], 247d)
28. God / C. Attitudes to God / 4. God Reflects Humanity
We cannot conceive of God, so we have to think of Him as an immortal version of ourselves [Plato]
     Full Idea: Because we have never seen or formed an adequate idea of a god, we picture him to ourselves as a being of the same kind as ourselves but immortal.
     From: Plato (Phaedrus [c.366 BCE], 246d)
28. God / C. Attitudes to God / 5. Atheism
There isn't a single reason for positing the existence of immortal beings [Plato]
     Full Idea: There is not a single sound reason for positing the existence of such a being who is immortal
     From: Plato (Phaedrus [c.366 BCE], 246d)
29. Religion / D. Religious Issues / 2. Immortality / a. Immortality
Soul is always in motion, so it must be self-moving and immortal [Plato]
     Full Idea: All soul is immortal, for what is always in motion is immortal. Only that which moves itself never ceases to be in motion.
     From: Plato (Phaedrus [c.366 BCE], 245c)