Month: September 2011
A very interesting study. Be sure to also check out Greene’s website wich has a lot of useful material.
Also, thanks to Gene Expression for letting me no about this study.
Edited to add
Here is the paper with the trick questions.
I red these today and needed an easy way to share them. Enjoy.
I am taking a metafysics class1 and last lectur’s topic was time travel. That is an issu i sort of like but i dislike the way people discuss it, in general. Ther is a widespred lack of clarity and lack of training in the relevant logics (that is, modal logics: alethic logic and temporal logic). A fine example of that is the first essay below.
The followup essay (2nd abov) is certainly better than the first but not quite clear enof to my taste. I do generally agree with Lewis tho. I advice people interested in the subject to lern alethic logic (S5) and read the following materials.
And for those who like fiction about time travel and wants to see som fiction with time travel that seems to be non-contradictory.
1Well, tecnically, i signed up for it but never turned up so far. I blame the timing. They put it at 0900, and even on the same day as another class (filosofical logic) altho not the same time. But it still implys that if i want to attend both lectures, then i hav to spend a lot of time on the university in one day. But i disfeel like spending that much time, unless ther is alcohol involved. :)
Somone requested this.
”Any attempt to deduce F propositions from M propositions
would perpetrate the fallacy of negating the antecedent, one of two
forms jokingly known as modus morons, The Way of the Moron.” (JENNY TEICHMAN – The Intellectual Capacity of David Stove)
I am taking an advanced logic class this semester. Som of the reading material has been posted in our internal system. I’ll post it here so that others may get good use of it as well. The text in question is John Nolt’s Logics chp. 11-12. I remade the pdfs so that they ar smaller and most of the text is copyable making for easyer quoting. Enjoy
Edit – A comment to the stuff (danish)
Dær står i Nolt kap. 12, at:
”We have said so far that the accessibility relation for all forms of alethic
possibility is reflexive. For physical possibility, I have argued that it is transitive as
well. And for logical possibility it seems also to be symmetric. Thus the accessibil-
ity relation for logical possibility is apparently reflexive, transitive, and symmetric.
It can be proved, though we shall not do so here, that these three characteristics
together define the logic S5, which is characterized by Leibnizian semantic… That
is, making the accessibility relation reflexive, transitive, and symmetric has the
same effect on the logic as making each world possible relative to each.” p. 343
mæn min entuisjon sagde maj strakes, at dette var forkert, altså, at de er forkert at
R1. For any world, that world relates to itself. (Reflexsive)
R2. For any world w1 and for any world w2, if w1 relates to w2, then w2 relates to w1. (Symmetry)
R3. For any world w1, for any world w2, and for any world w3, if w1 relates to w2, and w2 relates to w3, then w1 relates to w3. (Transitive)
er ækvivalænt mæd
R4. For any world w1 and for any world w2, w1 relates to w2. (Omni-relevans)
Mæn de er ganske rægtigt, at ves man prøver at køre diverse beviser igænnem, så kan man godt bevise fx (◊A→☐◊A) vha. en modæl som er reflexsive, symmetrical og transitive (jaj valgte 1r1, 2r2).
Mæn stadig er dær någet galt. Di forskællige verdener er helt isolerede, modsat vad di er i givet R4. Jaj googlede de, og andre har osse bemærket de:
”Requiring the accessibility relation to be reflexive, transitive and symmetric is to require that it be an equivalence relation. This isn’t the same as saying that every world is accessible from every other. But it is to say that the class of worlds is split up into classes within which every world is accessible from every other; and there is no access between these classes. S5, the system that results, is in many ways the most intuitive of the modal systems, and is the closest to the naive ideas with which we started.”