You talk a lot about samu in Zen. Does intellectual work count?
If you don't ever work with your hands you become too intellectual. Professors are too intelligent and can become a little bit crazy. Wisdom is not just a matter of the forebrain. True wisdom arises from both thalamus and hypothalamus. When both are strong you have great wisdom. But if you spend all of your time reading philosophy only your forebrain is working, while your old brain grows weak. The two are out of balance and you become tired and nervous and sometimes a little crazy. Your memory grows weaker and weaker, and even though the forebrain is developed by books, it grows tired.
When you start to grow old, you lose your memory. But through the hypothalamus, things are engraved in the brain. Their essence remains in the subconscious, and during zazen it revives. Not sexual ideas, not pleasant thoughts: the things that have made a profound impression on the body, they are what revive during zazen.
For me, the sutras, my master's talks, all those important things have marked not my memory, but my thalamus, through the subconscious. Accumulating facts to pass exams, on the other hand, was very hard work for me, and now I've forgotten them all.
During zazen, when I talk, the words penetrate to your thalamus and become seeds that will grow; in five, ten twenty years they will become wisdom. That is the highest psychology.
--from Questions To A Zen Master, by Taisen Deshimaru (1914-1982)
Additional books by Zen Master Deshimaru:
Za-Zen, The Practice of Zen
Sit: Zen Teachings of Master Taisen Deshimaru
The Ring of The Way-Testament of A Zen Master
The Zen Way To Martial Arts