David Ripley: Curry’s Paradox and Substructural Logic | Who Shaves the Barber? #51

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David Ripley

Consider the sentence C: “If this sentence is true, then David Ripley is a purple giraffe”. Suppose the sentence is true. Then the antecedent of the sentence (“this sentence is true”) is true. According to the inference rule modus ponens, if an if-then sentence (such as C) is true and its antecedent is true, then its consequent (“David Ripley is a purple giraffe”) must be true. It follows that if C is true, then David Ripley is a purple giraffe. But this conclusion is C: in other words, by simply supposing how things might turn out if C were true, we have proved that C, in fact, is true. So C is true, and since C’s antecedent is the claim that C is true, its antecedent is true as well. Now we can use modus ponens again to show that C’s consequent must be true. In other words, David Ripley really is a purple giraffe. QED.

This argument is Curry’s paradox. Obviously, the choice of “David Ripley is a purple giraffe” is arbitrary; a sentence of the form of “If this sentence is true, then X” can be used to prove any claim X. Now, in actual fact, David Ripley is not a purple giraffe, but a philosopher of language and logic. According to Ripley, solutions to paradoxes like Curry’s (as well as the Liar and the Sorites) fall into two broad categories: those that solve the paradoxes by messing with the meanings of important concepts (such as the meaning of “if-then”, truth, “not”, etc.) and those that solve them by changing the structural rules of inference by appeal to substructural logics.…

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Michael Hicks: Fiction-Directed Thought | Who Shaves the Barber? #49

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This is a fictional pipe.

I have a (true) thought that Sherlock Holmes lives on Baker Street. But what is this thought about? Is it about Sherlock Holmes? If so, is it about something that doesn’t exist? Can we really have thoughts about non-existent objects? What makes those thoughts true or false, if there is no object for the thought’s content to correspond to?

Philosopher Michael Hicks distinguishes fiction-directed thought from world-directed thought. A fiction-directed thought is knowingly about fiction; it is a kind of pretense. It is crucial that thoughts about fictional entities be fiction-directed. If if I think my “thought” about Sherlock Holmes is about a real person – in other words, if it is world-directed – then I don’t have a thought at all, because the ostensive object of my thought does not exist. According to Hicks, world-directed thought is “environment dependent”. It takes the intentional state and the object of the intentional state to make a thought. If the latter is missing, then there is no thought. Thoughts about fictional entities, as well as about hallucinations and other non-existent objects, must be fiction-directed in order to qualify as thoughts. Put another way, thought about fiction only successfully happens when we play a game of pretense set up by the author.

Be sure to listen to part 1 of this interview first.

If you’re interested in the metaphysics of thought, I discuss higher-order thoughts in this interview with David Rosenthal.…

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Michael Zigismund: Philosophy of Law | Who Shaves the Barber? #22

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Before the law, there is the philosophy of law

What is the law? Is it simply what’s to be found in legal statutes and government decrees? Or is it something broader, affected by and inseparable from both morality and custom?

This is one of the fundamental debates in philosophy of law. On one side stand the positivists, who propose a narrow view of the law as separate from ethics and other concerns outside of the direct commands of the state. On the other, we have natural rights theorists, who believe the law and morality are inseparable. Indeed, according to natural rights theorists, illegitimate laws aren’t laws at all.

On what grounds may this debate be settled? And what’s really at stake here? Is there more to this than a question of semantics? Legal expert Michael Zigismund guides us through this debate, and applies it to three areas: Nazi law, slavery, and gun ownership. He concludes with a summary of a “third way”, which he argues takes the best of both while avoiding their pitfalls: the Hayekian view of law as emergent practice.

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Special thanks to Jackie Blum for the podcast art, and The Tin Box for the theme music.

Topics discussed

0:20 – Introduction to Michael Zigismund
2:02 – What is law?
8:53 – Common law v. customary law
11:36 – Positivism v. natural law
16:45 – Is Nazi law law?
19:23 – Separation thesis
22:54 – Application to federalism
26:14 – Where does morality of law come from?…

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