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@LogicPractice

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Logic and applications of logic from @JohnDCook

Houston, TX
Joined September 2016
Don't wanna be here? Send us removal request.
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@LogicPractice
Logic & Applications
2 years
Big logic
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@LogicPractice
Logic & Applications
1 year
When a logician receives a wedding invitation
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"What is a tautology?" "A tautology is a tautology."
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3 years
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@LogicPractice
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Ran across an author who says “precisely when” rather than “if and only if.” I kinda like that.
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@LogicPractice
Logic & Applications
1 year
Gödel's completeness theorem (1929) isn't as famous as his incompleteness theorem (1931).
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@LogicPractice
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2 years
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@LogicPractice
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11 months
'Ex falso quodlibet.' From a false assumption, anything follows.
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@LogicPractice
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2 years
Gödel's completeness theorem (1929) isn't as famous as his incompleteness theorem (1931).
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@LogicPractice
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8 years
"You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic." -- Robert A. Heinlein
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@LogicPractice
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1 year
All consistent axiomatic formulations of number theory include undecideable propositions. -- Kurt Gödel
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@LogicPractice
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8 years
"Logic has turned out to be significiantly more effective in computer science than it has been in mathematics."
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'Logic has turned out to be significantly more effective in computer science than it has been in mathematics.' [pdf]
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@LogicPractice
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8 years
Tarski's undefinability theorem
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@LogicPractice
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2 years
“One should never try to prove anything that is not almost obvious.” ― Alexander Grothendieck
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@LogicPractice
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11 months
Modal logic axiom cube
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@LogicPractice
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4 years
Q: How many modal logicians does it take to change a lightbulb? A: In which world?
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@LogicPractice
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1 year
Gödel's compactness theorem: A first order theory T is satisfiable iff every finite subset of T is satisfiable.
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@LogicPractice
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1 year
'Induction makes you feel guilty for getting something out of nothing ... but it is one of the greatest ideas of civilization.' -- Herbert Wilf
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@LogicPractice
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1 year
Gödel proved in 1932 that intuitionistic logic has no interpretation as a finite-valued logic. The proof was only two pages long.
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@LogicPractice
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1 year
Peirce's law: ((P => Q) => P) => P. Holds in classical logic but not intuitionistic logic.
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@LogicPractice
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3 years
'Logic has turned out to be significantly more effective in computer science than it has been in mathematics.' [pdf]
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@LogicPractice
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11 months
'It requires a very unusual mind to undertake the analysis of the obvious.' -- Alfred North Whitehead
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@LogicPractice
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2 years
“It wouild be very discouraging if somewhere down the line you could ask a computer if the Riemann hypothesis is correct and it said, `Yes, it is true, but you won’t be able to understand the proof.’” — Ronald Graham
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@LogicPractice
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“When you have eliminated the impossible, whatever remains is often more improbable than your having made a mistake in one of your impossibility proofs.” -- Steven Kass
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@LogicPractice
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11 months
“It is not easy, and perhaps not even useful, to explain briefly what logic is.' -- E. J. Lemmon
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@LogicPractice
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2 years
"No science can defend its own first principles." -- Aristotle (384–322 BC)
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@LogicPractice
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1 year
Incomplete and Utter Introduction to Modal Logic
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@LogicPractice
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'You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.' -- Robert A. Heinlein
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@LogicPractice
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1 year
'Logic, like whiskey, loses its beneficial effect when taken in too large quantities.' -- Edward Plunkett
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@LogicPractice
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1 year
'A proof tells us where to concentrate our doubts.” — Morris Kline
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2 years
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@LogicPractice
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The linear logic connectives ⊕ and & are called additive, ⊗ and ⅋ are called ``multiplicative,'' and ! and ? are called ``expontentials.'' The equations below are analogous to the equation exp(a + b) = exp(a) exp(b).
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@LogicPractice
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'Induction makes you feel guilty for getting something out of nothing ... but it is one of the greatest ideas of civilization.' -- Herbert Wilf
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@LogicPractice
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4 years
"Logic, like whiskey, loses its beneficial effect when taken in too large quantities." Edward Plunkett
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@LogicPractice
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3 years
Logic gate symbols for AND, OR, and XOR on top row. Their negations NAND, NOR, and XNOR on bottom row.
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@LogicPractice
Logic & Applications
5 years
"It requires a very unusual mind to undertake the analysis of the obvious." -- Alfred North Whitehead
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@LogicPractice
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3 years
Gödel proved in 1932 that intuitionistic logic has no interpretation as a finite-valued logic. The proof was only two pages long.
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@LogicPractice
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3 years
Logicians put their assumptions on the left side of a turnstile symbol. Statisticians put their assumptions on the right side of a vertical bar.
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@LogicPractice
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@LogicPractice
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3 years
Gödel's compactness theorem: A first order theory T is satisfiable iff every finite subset of T is satisfiable.
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@LogicPractice
Logic & Applications
2 years
“When you have eliminated the impossible, whatever remains is often more improbable than your having made a mistake in one of your impossibility proofs.” -- Steven Kass
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@LogicPractice
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1 year
Glivenko's theorem: If φ is a propositional formula, then φ is a classical tautology if and only if ¬ ¬ φ is an intuitionistic tautology.
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@LogicPractice
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5 years
'Ex falso quodlibet.' From a false assumption, anything follows.
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@LogicPractice
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2 years
The linear logic connectives ! and ? are pronounced 'of course' and 'why not'.
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@LogicPractice
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5 years
'Informal proofs are algorithms; formal proofs are code.'
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@LogicPractice
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3 years
“When you have eliminated the impossible, whatever remains is often more improbable than your having made a mistake in one of your impossibility proofs.” -- Steven Kass
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@LogicPractice
Logic & Applications
6 years
"Logic has turned out to be significantly more effective in computer science than it has been in mathematics." [pdf]
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@LogicPractice
Logic & Applications
1 year
The linear logic connectives ! and ? are pronounced 'of course' and 'why not'.
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@LogicPractice
Logic & Applications
3 years
Glivenko's theorem: If φ is a propositional formula, then φ is a classical tautology if and only if ¬ ¬ φ is an intuitionistic tautology.
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@LogicPractice
Logic & Applications
3 years
“One should never try to prove anything that is not almost obvious.” ― Alexander Grothendieck
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@LogicPractice
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11 months
Classic papers in programming languages and logic
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@LogicPractice
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3 years
'You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.' -- Robert A. Heinlein
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@LogicPractice
Logic & Applications
7 years
“Before functorality, people lived in caves.” -- B. Conrad Category theory is a great source of arrogant quotes, sometimes tongue-in-cheek.
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@LogicPractice
Logic & Applications
2 years
Gödel's completeness theorem (1929) isn't as famous as his incompleteness theorem (1931).
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@LogicPractice
Logic & Applications
7 years
'You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.' -- Robert A. Heinlein
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@LogicPractice
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2 years
Gödel proved in 1932 that intuitionistic logic has no interpretation as a finite-valued logic. The proof was only two pages long.
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@LogicPractice
Logic & Applications
3 years
'Ex falso quodlibet.' From a false assumption, anything follows.
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@LogicPractice
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2 years
'It requires a very unusual mind to undertake the analysis of the obvious.' -- Alfred North Whitehead
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@LogicPractice
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1 year
Kurt Gödel Created a hurdle For the truths of a system: You just can't list 'em! -- Steven Cushing
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8 years
Hacker-Proof Code
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3 years
Linear logic analogies to arithmetic
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@LogicPractice
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'Every good idea will be discovered twice: once by a logician and once by a computer scientist.' -- @PhilipWadler
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@LogicPractice
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11 months
In linear logic, the implication A -> B can be read 'consuming A produces B.' Sometimes written with the 'lollipop' symbol for linear implication.
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@LogicPractice
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3 years
“Attempts to form social judgments by aggregating individual expressed preferences always lead to the possibility of paradox.” — Kenneth Arrow
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@LogicPractice
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10 months
'Logic, like whiskey, loses its beneficial effect when taken in too large quantities.' -- Edward Plunkett
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@LogicPractice
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2 years
'A proof tells us where to concentrate our doubts.” — Morris Kline
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@LogicPractice
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7 years
Ask three modal logicians what modal logic is, and you are likely to get at least three different answers. -- Blackburn et al
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@LogicPractice
Logic & Applications
6 years
Gödel proved in 1932 that intuitionistic logic has no interpretation as a finite-valued logic. The proof was only two pages long.
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@LogicPractice
Logic & Applications
8 years
'Informal proofs are algorithms; formal proofs are code.'
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@LogicPractice
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2 years
'Induction makes you feel guilty for getting something out of nothing ... but it is one of the greatest ideas of civilization.' -- Herbert Wilf
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@LogicPractice
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1 year
History of modal logic [pdf]
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@LogicPractice
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2 years
Karnaugh maps are a way to simplify boolean algebra expressions.
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8 years
Formal verification and The Martian
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“I wish my wish would not be granted!” — Douglas Hofstadter
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@LogicPractice
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5 years
'You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.' -- Robert A. Heinlein
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@LogicPractice
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1 year
A Timeline for Logic, λ-Calculus, and Programming Language Theory by Dana Scott [pdf]
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@LogicPractice
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5 years
Gödel, Leibniz, and God
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@LogicPractice
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2 years
'Logic, like whiskey, loses its beneficial effect when taken in too large quantities.' -- Edward Plunkett
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@LogicPractice
Logic & Applications
2 years
Peirce's law: ((P => Q) => P) => P. Holds in classical logic but not intuitionistic logic.
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@LogicPractice
Logic & Applications
5 years
Gödel proved in 1932 that intuitionistic logic has no interpretation as a finite-valued logic. The proof was only two pages long.
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@LogicPractice
Logic & Applications
1 year
The halting problem: You cannot write a program that can tell whether an arbitrary program will complete or run forever.
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2 years
Triangles of dots in LaTeX
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@LogicPractice
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2 years
“One should never try to prove anything that is not almost obvious.” ― Alexander Grothendieck
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1 year
A modal logic is monotone if □(p∧q) → □p.
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8 years
'You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.' -- Robert A. Heinlein
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@LogicPractice
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Modal logic duality
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4 years
“It cannot be a complete coincidence that several outstanding logicians of the twentieth century found shelter in asylums at some time in their lives.” — Gian-Carlo Rota
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@LogicPractice
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1 year
Löb's theorem regarding Peano arithmetic is taken as an axiom in Gödel–Löb modal logic. □(□p → p) → □p.
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@LogicPractice
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1 year
“One should never try to prove anything that is not almost obvious.” ― Alexander Grothendieck
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@LogicPractice
Logic & Applications
2 years
'Ex falso quodlibet.' From a false assumption, anything follows.
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