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Sep 13, 2011 at 20:06 comment added HNuer @jlk Also in order for your assertion that the general section meets the fibers $f^{-1}(x)$ and $f^{-1}(y)$ from a dimension count, I believe you also need that dim $X\geq 2$. You don't just need it to define the blow-up, unless you had some other dimensional reason in mind, which I'd like to here. Thanks for the nice answer.
Sep 13, 2011 at 19:36 comment added jlk @MP: Your remark reminded me that in my proof sketch, I should have stated at the beginning "We can assume the dimension of $X$ is at least $2$." No suitable blow-up exists if $X$ is a single point...
Sep 13, 2011 at 19:35 history edited jlk CC BY-SA 3.0
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Sep 13, 2011 at 16:23 comment added M P Maybe less tautologically: if the singular locus of $X$ is the support of an ample divisor, then you are probably in trouble.
Sep 13, 2011 at 16:22 comment added M P To answer your question: if $X$ is itself a singular curve!
Sep 13, 2011 at 16:18 history edited jlk CC BY-SA 3.0
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Sep 13, 2011 at 16:11 history answered jlk CC BY-SA 3.0