In our daily life, those of us who are not yet enlightened exist as a smear between our actions and our recursive thoughts about our actions. We do things - and think about doing those things, as we do them. We are, in that sense, removed from the visceral reality of our life.
This is thought.
To achieve mu-thought, unfortunately, cannot be done simply by not thinking. Not thinking may itself be a goal, at times (in zazen, perhaps). But un-thought isn't the opposite of thought, or the absence of thought. It is what is when there isn't a thing such as thought, anywhere.
I envision it as a collapsing of our selves into one, coherent, unified, cohesive, unitary self. It is the moment when, perhaps by accident, we experience the transcendence of true enlightenment. This is merely my own ideas, nothing formal. Sometimes, this comes from pure focus on a task. Sometimes, from utter fear and the proximity of death. Sometimes, perhaps, from chemical modifications to our brains, for a little while. I have experienced all of these forms of mu-thought, and all have been. . . away.
Also, as I have experienced recently, un-thought can come from total and comprehensive grief, a grief so profound that the self simply vanishes, for a time. There is no thought, or lack of thought - there is pain, and beyond the pain is the place where there are no words or ideas. It is startling, and exhausting, and liberating, and frightening.
A pure form of mu-thought is, of course, achieved during orgasm. I may be thinking, prior to that point, about how much I love my partner - how his joy and love is echoing off my own, how the beauty of this ennobles both of us. I may be thinking I want to wait, to prolong his pleasure further - or I may be thinking, frankly, that I have so much work to do and I should go ahead and let go so I can get back to "real" tasks. Thought is like that, it outruns us.
But when orgasm presents itself, these thoughts do not exist. They aren't gone, but rather. . . part of a different reality, for a brief moment. I collapse, myselves, into one single point - an emotional event horizon. It all stops, then goes away. It lasts a moment, and forever. I have my suspicions that they find much wisdom, there. They won't tell me, either way.
It is mu-thought, and there is no recursion.
In literary symbolism, the male orgasm is "the little death" (female orgasm seems to be mostly ignored by the old goats of Western literature - not fair, but true, Sappho perhaps being the exception - though not much of an old goat, herself). And in death is perhaps the purest form of un-thought. Non-existence. Transcendence.
Male canines don't have a point-specific orgasm. Their orgasm is continuous and may go from 10 minutes to more than 45 minutes (depending largely on breed of dog). This is a profound state of experience - well, it looks like it to me at least. I do not know if it results in mu-thought throughout, but I strongly suspect it does. Like us, dogs can think themselves into dark corners during everyday life. Like us, they revel in the freedom from self-referentiality. Unlike us, their transcendence of that state is measured not in seconds but in fractions of an hour.
Peace,
Fausty