I keep all Halachah but I don’t know of any rational (this world) reason or benefit for most of it. Why do I keep it then? Because I believe firmly that God dictated the entire Torah word for word, and all the Bible Academics are wrong. Also I believe the world is 6,000 years old, Adam was the first ever man, and all the Scientists are wrong. Furthermore, I can prove all of this with various proofs. And if anyone ever proved me to that these beliefs were false I would drop all of it in a minute. But of course that’s never going to happen.
I keep all Halachah because I can see the rational benefits of doing so, at least for most of it. As for the rest, it’s mostly minor details, and its perceived usefulness varies from person to person. Since it’s an ancient tradition that has been going for thousands of years, I’m very reluctant to mess with it. Was the Torah written by God? Probably not. Was it Divinely Inspired? Who can say? There’s no way of determining that. But Judaism has a long and venerable history, we have achieved great things, and I perceive Orthodox Judaism to be highly moral in general and a great community and lifestyle. Of course it’s not perfect, but it’s better than the alternative. The question of how exactly 'Divinely Inspired' it all is doesn't bother me, because either way it's a valuable system, and I'm extremely proud to be part of the traditional Jewish community, for rational reasons alone.
Lifted whole cloth, from XGH, who concludes with this:
For some strange reason, a few of my commenters think that Person B is not viable or sustainable as a community, but Person A is going mechoyil ad choyil.I agree with his commenters, but not for theological reasons. I'm far more pragmatic, and its clear to me the game is fixed. Marc Steyn, author of the lovely obituaries that appear on the last page of every edition of the Atlantic, famously says that the future belongs to the fecund and confidant. I'm not sure Person A is confidant - can a community that defines itself against everyone else, while stifling questions and punishing non-conformity be called confident? - but there's no doubt he knows how to breed.