In the comments section of my last piece Rob Myers said, “My teacher, Jisho Warner (no relation) says ‘You can sit in a chair; it’s just harder.’” That’s true. One of the most important points in zen practice is keeping the spine straight with little or — preferably — no support. It’s a balancing act, like riding a bicycle. There’s a reason bicycles aren’t built with comfy reclining chairs on them. You’d fall over.
When you sit with your back against a chair, you are robbing yourself of that feeling of physical balance. And whenever I’ve attempted to do something like zazen in a chair, the chair has forced its own ideas of balance upon my body. There is no tilt to the pelvis and therefore no way to make the spine balance on its own.
Those kneeling chairs they make for people who work on computers all day can be modified to make a decent compromise. Because it’s not really about how you screw up your legs. You don’t have to sit in the full lotus position (I predict in the future at least 27 more people will say, “Brad Warner says you have to sit in the full lotus position” even after I say you don’t 39 more times). It’s just that the full lotus position creates a really, really stable base for the spine. There is a very good reason it’s been a favorite for around 3000 years. Still, there may be other slightly less efficient but still acceptable ways to get the spine to balance.
The standard straight backed chairs you get at the local Furniture Hut are just not one of them. If you really honest to goodness need to sit on a chair you’ll have to work a lot harder at zazen than those who sit on cushions on the floor.