Timeline for An exercise in Kunen. Getting Axiom of Replacement from set-like transitive closure.
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| May 6, 2012 at 23:38 | comment | added | Joel David Hamkins | Gerhard, I'll gladly read what you write on meta, since I understand that people have differing opinions on this issue. | |
| May 6, 2012 at 16:37 | comment | added | Gerhard Paseman | Ali, I am glad that you find Prof. Hamkins response appropriate to your situation. If I knew what you had tried and how you were stumbling, I might or might not continue with the Socratic method. As your post was presented, a Socrratic response seemed appropriate to me. One of my fears is that other students will not derive as much benefit from Joel's answer as they would from an appropriate question or hint. It may be a matter of pedagogy and not of mathematics. I intend to follow up this issue with a meta..mathoverflow post. Gerhard "Not A Professor By Choice" Paseman, 2012.05.06 | |
| May 6, 2012 at 9:04 | vote | accept | Ali Kare | ||
| May 6, 2012 at 9:00 | comment | added | Ali Kare | @ Prof. Paseman: Sometimes it is a good student who already knows the topic but nevertheless gets stuck at an easy problem. It happens. I've already worked on it long enough and unfortunately I do not have any more time to spare. So please do not prolong my misery by subjecting me to the socratic method. It is already embaressing for me to ask such a simple question. What I need is to be shown the answer so that I can see what I missed and move on. I guarentee you that I will learn from the answer given, especially because I am upset that I couldn't think of it myself. | |
| May 6, 2012 at 8:58 | comment | added | Ali Kare | @ Professor Hamkins: Thank you for taking your time to answer my question. You have been most helpful. | |
| May 6, 2012 at 1:04 | comment | added | Gerhard Paseman | I will visit the meta thread and suggest an alternate approach there. Thank you for the response Joel. Gerhard "Not Yet Agreeing To Disagree" Paseman, 2012.05.05 | |
| May 6, 2012 at 0:17 | comment | added | Joel David Hamkins | I don't agree with that perspective, Gerhard. (See meta.math.stackexchange.com/a/1661/413 for a further explanation of my views.) If someone asks a good math question, as here, then we should simply try to give the best possible answer. Math.SE in particular has numerous instances of totally unsatisifying half-answers to questions, in the style you suggest, but I find them simply to be poor answers. Let a student try hard on his or her own, but when they come for assistance, let us all try to give the best answer we possibly can, mustering whatever elegance and clarity we are able. | |
| May 6, 2012 at 0:05 | comment | added | Gerhard Paseman | Nice spolier. May I suggest in future less explicit answers for text exercises so the poster has more to do? e.g. "See if you can find a set-like class relation R so that R* will yield a set containing the desired set in the replacement axiom; for starters, you could have R(x,y) for every x in X such that there is a unique y so that phi(x,y,z), where phi is the formula used in the replacement axiom with some parameter z; what else would keep R set-like and have R* help you to show (y | there is x in X such that phi(x,y,z) ) is a set?" Gerhard "Ask Me About System Design" Paseman, 2012.05.05 | |
| May 5, 2012 at 23:56 | history | edited | Joel David Hamkins | CC BY-SA 3.0 |
fixed direction of the relation; added 80 characters in body
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| May 5, 2012 at 23:48 | history | edited | Joel David Hamkins | CC BY-SA 3.0 |
added 3 characters in body
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| May 5, 2012 at 23:41 | history | answered | Joel David Hamkins | CC BY-SA 3.0 |