JL;DR SUMMARY Jenna Weissman Joselit provides a comprehensive and critical look at Mordecai Kaplan, the founder of Reconstructionist Judaism, in her new biography, "Kaplan Unbound." A way out west there was a fella, fella I want to tell you about, fella by the name of Jeff Lebowski. At least, that was the handle his lovin' parents gave him, but he never had much use for it himself. This Lebowski, he called himself the Dude. Now, Dude, that's a name no one would self-apply where I come from. But then, there was a lot about the Dude that didn't make a whole lot of sense to me. And a lot about where he lived, likewise. But then again, maybe that's why I found the place s'durned innarestin'.