[..]especially when I'm the only leader, I climb in check. I want to be reasonably certain that I can lead every pitch without difficulty. I know that some partners aren't as well equipped to deal with issues that may arise. If I decide to take someone like that up a multipitch route, the burden of responsibility is mine. I'll dial back the difficulty and have a more casual climbing day.

There's a difference between a weaker partner who can lead and one who can't. I've climbed with partners who, at the time, couldn't lead free pitches as hard as I could. They were certainly competent climbers, so I never thought there was anything to be concerned about.

This viewpoint was tested many years ago when we were caught in a sudden and very severe summer storm. The entire face turned into a waterfall. I was tied in short in a shallow groove and belaying my partner when the storm hit, and had to crane my head to keep it out of the water---the rest of my body was in the flow. By the time my partner reached the belay (with lots of tension from me since he was climbing in a waterfall the whole time) I was seriously hypothermic and suffering from extreme full-body muscle cramps. The struggles of climbing plus the fact that he had the pack and so had been able to put on raingear kept him warm.

I was supposed to lead every pitch, but that was out of the question now. But no worries, my partner improvised some aid slings for the hardest moves and lead on. (Going down at that point would have been much harder.) The rain stopped and after two or three pitches I warmed up again and was able to over the lead. The net effect was nothing more than being a little slower than planned because of the aid climbing.

I have climbed and continue to climb with partners who could follow and belay but who really don't lead at all, and I've done this in very remote areas as well as at the local crag. This is essentially guiding, and I think a modified soloing mentality is in order---you absolutely cannot make any leading mistakes and you have to have the confidence of a soloist or you probably shouldn't be doing it. (I use the word "modified" because short leader falls onto good pro are conceivable and do not constitute a "leading mistake" in this context.)

In this situation, the second cannot take over the lead. I think there is one moral imperative: if the climbing is at all remote, the leader insure that the second is competent enough to save themselves if something really bad happens. This means the second must at the very least be able to set up and execute multiple rappels and know enough about natural and gear anchors to give them a good chance of getting down by themselves.

Beyond that, fancy self-rescue techniques are of course good to know. But the ability to use them in the field, under stress, will depend on having put in a significant amount of practice time, which is something not everyone has either the time or the inclination to do. And many self-rescue procedures will not be effective under all circumstances and will expose the party (and in particular the second) to considerable additional risks.

I say this not to knock self-rescue (which, however, I believed to be way over-hyped), but because people who are embracing situations in which only one party member can lead ought to do so with a clear understanding of what they doing and what the implications are.

There's a difference between a weaker partner who can lead and one who can't.

Thanks you all for your considered replies, and rgold especially as you address my concerns very closely. Yes, my partner is by no means a weaker climber than me - but he doesn't lead. Several of you confirm my unease with the situation. Before we get into doing anything remotely serious we'll book in for a guided weekend (we have an AMGA-certified guide here in Tokyo, a very competent young guy) focussing on self-rescue and emergency situations, especially incapacitated leader scenarios. I'll also have a bit of a heart-to-heart with my partner about why he doesn't want to lead and see if given the safety advantages for both of us, he will give it a try, at least on easy pitches.

rgold, I'll track down your posts re self-rescue, am interested in your perspective on this.

Thanks all.

There's a difference between a weaker partner who can lead and one who can't. I've climbed with partners who, at the time, couldn't lead free pitches as hard as I could. They were certainly competent climbers, so I never thought there was anything to be concerned about.

Beyond that, fancy self-rescue techniques are of course good to know. But the ability to use them in the field, under stress, will depend on having put in a significant amount of practice time, which is something not everyone has either the time or the inclination to do. And many self-rescue procedures will not be effective under all circumstances and will expose the party (and in particular the second) to considerable additional risks.

I say this not to knock self-rescue (which, however, I believe to be way over-hyped), but because people who are embracing situations in which only one party member can lead ought to do so with a clear understanding of what they doing and what the implications are.

[Edited for typos---twice.]