In reply to John_Hat:
> (In reply to phja)
>
> Religious argument position 1: Double fishermans, with any variety of knot in the middle (my preferred option is reef knot). Chances of knot failure - nil. In repeated tests the rope breaks before the knot.
>
> Religious argument position 2: Double overhand. Argument is that is doesn't tend to get stuck in cracks as much as a double fishermans.
>
> This (rather excessively extensive test) may help.
>
>
http://user.xmission.com/~tmoyer/testing/EDK.html
>
> Which basically says that fishermans is bombproof, fig-8 is lethal, and overhand is somewhere in between, but practiaclly is unlikely to give any problems unless badly tied. However if it is badly tied (possible?) then there might be a problem.
You're being fairly misleading here. First you talk about the double overhand then you post a site with testing pertaining to a single overhand (edk). If I get some figures up for a single fisherman does that make the double fisherman more dangerous? Very odd.
The best knot is probably neither/experience and knowledge of different knots and their properties. Stating "I use X knot and I won't listen to anything else" is deciding to be ignorant. There are tested knots/variants which are flat and have superior breaking strength than the overhand/better profile than the double fishermans. Whatever knots you know, It's wise to use the knot appropriate to the situation. Doublefisherman for wet/icy ropes, double overhand in fair conditions for speed and ease of tying (just one example).
This goes for all things in climbing, if you are comfortable (important) with several methods of doing things you can adapt more easily to a given situation. I don't think religious dogma comes into it. We rationalise our decisions (or at least i do).