Combining Philosophers

All the ideas for Eubulides, Augustus De Morgan and St Mark

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7 ideas

5. Theory of Logic / E. Structures of Logic / 6. Relations in Logic

17744	De Morgan started the study of relations and their properties [De Morgan, by Walicki]
	Full Idea: De Morgan started the sustained interest in the study of relations and their properties.
	From: report of Augustus De Morgan (On the Syllogism IV [1859]) by Michal Walicki - Introduction to Mathematical Logic History D.1.1

13501	De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [De Morgan, by Hart,WD]
	Full Idea: There was a prejudice against relations (in favour of properties) but De Morgan and others that impeccable inferences turn on relations and elude Aristotle's syllogistic. Thus: All horses are animals. Hence, all heads of horses are heads of animals.
	From: report of Augustus De Morgan (On the Syllogism IV [1859]) by William D. Hart - The Evolution of Logic 4
	A reaction: This is actually an early example of modern analytic philosophy in action. You start with the inferences, and then work back to the ontology and the definition of concepts. But in pinning down such concepts, do we miss their full meaning?

5. Theory of Logic / G. Quantification / 2. Domain of Quantification

17743	De Morgan introduced a 'universe of discourse', to replace Boole's universe of 'all things' [De Morgan, by Walicki]
	Full Idea: In 1846 De Morgan introduced the enormously influential notion of a possibly arbitrary and stipulated 'universe of discourse'. It replaced Boole's original - and metaphysically a bit suspect - universe of 'all things'.
	From: report of Augustus De Morgan (works [1846]) by Michal Walicki - Introduction to Mathematical Logic History D.1.1
	A reaction: This not only brings formal logic under control, but also reflects normal talk, because there is always an explicit or implicit domain of discourse when we talk. Of virtually any conversation, you can say what it is 'about'.

5. Theory of Logic / L. Paradox / 1. Paradox

6007	If you know your father, but don't recognise your father veiled, you know and don't know the same person [Eubulides, by Dancy,R]
	Full Idea: The 'undetected' or 'veiled' paradox of Eubulides says: if you know your father, and don't know the veiled person before you, but that person is your father, you both know and don't know the same person.
	From: report of Eubulides (fragments/reports [c.390 BCE]) by R.M. Dancy - Megarian School
	A reaction: Essentially an uninteresting equivocation on two senses of "know", but this paradox comes into its own when we try to give an account of how linguistic reference works. Frege's distinction of sense and reference tried to sort it out (Idea 4976).

5. Theory of Logic / L. Paradox / 6. Paradoxes in Language / a. The Liar paradox

6006	If you say truly that you are lying, you are lying [Eubulides, by Dancy,R]
	Full Idea: The liar paradox of Eubulides says 'if you state that you are lying, and state the truth, then you are lying'.
	From: report of Eubulides (fragments/reports [c.390 BCE]) by R.M. Dancy - Megarian School
	A reaction: (also Cic. Acad. 2.95) Don't say it, then. These kind of paradoxes of self-reference eventually lead to Russell's 'barber' paradox and his Theory of Types.

5. Theory of Logic / L. Paradox / 6. Paradoxes in Language / b. The Heap paradox ('Sorites')

6008	Removing one grain doesn't destroy a heap, so a heap can't be destroyed [Eubulides, by Dancy,R]
	Full Idea: The 'sorites' paradox of Eubulides says: if you take one grain of sand from a heap (soros), what is left is still a heap; so no matter how many grains of sand you take one by one, the result is always a heap.
	From: report of Eubulides (fragments/reports [c.390 BCE]) by R.M. Dancy - Megarian School
	A reaction: (also Cic. Acad. 2.49) This is a very nice paradox, which goes to the heart of our bewilderment when we try to fully understand reality. It homes in on problems of identity, as best exemplified in the Ship of Theseus (Ideas 1212 + 1213).

28. God / B. Proving God / 3. Proofs of Evidence / e. Miracles

20716	False prophets will perform wonders to deceive even the elect [Mark]
	Full Idea: For false messiahs and false prophets will appear and perform signs and wonders to deceive, if possible, even the elect.
	From: St Mark (02: Gospel of St Mark [c.66], 13:22), quoted by Brian Davies - Introduction to the Philosophy of Religion
	A reaction: This casts a rather different light on the miracles of Jesus, since they were performed in a context in which even Jesus believed that lots of people (and not just the son of God) could perform miracles. Undermines any Argument from Miracles.