Combining Texts

Ideas for 'Parmenides', 'Rationality and Logic' and 'Meditations'

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8 ideas

2. Reason / F. Fallacies / 1. Fallacy
'Denying the antecedent' fallacy: φ→ψ, ¬φ, so ¬ψ [Hanna]
     Full Idea: The fallacy of 'denying the antecedent' is of the form φ→ψ, ¬φ, so ¬ψ.
     From: Robert Hanna (Rationality and Logic [2006], 5.4)
'Affirming the consequent' fallacy: φ→ψ, ψ, so φ [Hanna]
     Full Idea: The fallacy of 'affirming the consequent' is of the form φ→ψ, ψ, so φ.
     From: Robert Hanna (Rationality and Logic [2006], 5.4)
We can list at least fourteen informal fallacies [Hanna]
     Full Idea: Informal fallacies: appeals to force, circumstantial factors, ignorance, pity, popular consensus, authority, generalisation, confused causes, begging the question, complex questions, irrelevance, equivocation, black-and-white, slippery slope etc.
     From: Robert Hanna (Rationality and Logic [2006], 7.3)
2. Reason / F. Fallacies / 4. Circularity
Circular arguments are formally valid, though informally inadmissible [Hanna]
     Full Idea: A circular argument - one whose conclusion is to be found among its premises - is inadmissible in most informal contexts, even though it is formally valid.
     From: Robert Hanna (Rationality and Logic [2006], 2.1)
     A reaction: Presumably this is a matter of conversational implicature - that you are under a conventional obligation to say things which go somewhere, rather than circling around their starting place.
It is circular to make truth depend on believing God's existence is true [Arnauld on Descartes]
     Full Idea: How does the author avoid reasoning in a circle when he says that we are sure that what we clearly and distinctly perceive is true only because God exists? But we can be sure that God exists only because we clearly and distinctly perceive this.
     From: comment on René Descartes (Meditations [1641], §5.71) by Antoine Arnauld - Objections to 'Meditations' (Fourth) 214
Descartes is right that in the Christian view only God can guarantee the reliability of senses [Nietzsche on Descartes]
     Full Idea: Even Descartes had a notion that in a Christian mode of thought (where God is a good creator), only God's veracity guarantees to us the judgements of our senses.
     From: comment on René Descartes (Meditations [1641], §5.71) by Friedrich Nietzsche - The Will to Power (notebooks) §436
     A reaction: An unusual defence of the notorious Cartesian Circle. Of course, Descartes claims that God guarantees reason (as 'clear and distinct conception'), not senses, and only reason led Descartes to God.
Once it is clear that there is a God who is no deceiver, I conclude that clear and distinct perceptions must be true [Descartes]
     Full Idea: Once I perceived that there is a God,…and that he is no deceiver, I then concluded that everything that I clearly and distinctly perceived is necessarily true.
     From: René Descartes (Meditations [1641], §5.70)
     A reaction: spotted by Arnauld
2. Reason / F. Fallacies / 5. Fallacy of Composition
Formally, composition and division fallacies occur in mereology [Hanna]
     Full Idea: Informal fallacies of composition and division go over into formal fallacies of mereological logic.
     From: Robert Hanna (Rationality and Logic [2006], 7.3)