For example the field of real numbers forms a structure R whose elements are the real numbers, with signature consisting of the individual constant 0 to name the number zero, a 1-ary function symbol - for minus, and two 2-ary function symbols + and . for plus and times. At first sight we can't add a symbol to express 1/x, since all the named functions have to be defined on the whole domain of the structure, and there is no such real number as 1/0. But on second thoughts this is not a serious problem; any competent mathematician puts the condition ‘x is not zero’ before dividing by x, and so it never matters what the value of 1/0 is, and we can harmlessly take it to be 42. But most model theorists are uncomfortable with any kind of division by zero, so they stick with plus, times and minus.
Schlagwort: Logik
42.
But maybe of.
There's definitely, definitely, definitely no logic
To human behaviour
Grandpas neither.
Killing Grandmothers should not be allowed.
Sonja Smets about David Lewis about Time Travel
"Logics" are not logic.
We misunderstand logic if we think there are "logics" among which we could somehow choose. There is reasoning. Specific formal systems may or may not adequately capture aspects of correct reasoning. But there is no neutral place outside logic from which to decide what "logic" to adopt.
Allan Stairs rephrasing Kripke against Putnam
Innocent question.
What's your background?
$teacher