Tag Archives: topos theory

The definition of toposes has surprisingly powerful consequences. (For example, toposes have all finite colimits.) Probably the best analogy elsewhere in which a couple of mild-sounding hypotheses pick out a very narrow and interesting class of examples is the way … Continue reading

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The ontological commitment of a sentence is whatever must be among the values of bound variables for the sentence to come out as true. Willard van Orman Quine I bring up this quotation not to agree or disagree with Quine, … Continue reading

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http://www.cs.ox.ac.uk/quantum/talksarchive/clap1/clap1-chrisisham.avi Is there really such a thing as a point? Well, not really…. Ask any of our undergraduates, why the real numbers? Can you say there’s something √π centimetres away from here?—Well, not really, it’s an approximation….—An approximation to what? “We’re not … Continue reading

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“Have you ever done acid, kid? This book is like Acid.” —John L. Rhodes, speaking of the book Topos Theory by Peter Johnstone (Source: http://www.amazon.com/gp/product/0521337798?ie=UTF8&tag=hiremebecauim-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0521337798)

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The axiom of choice need not hold in a topos, and the law of the excluded middle need not hold. John Baez more, much more: toposes, triples and theories (full book pdf)

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