Zazen

Zazen is:

"Neither trying to think nor trying not to think;
"Just sitting with no deliberate thought."

I have been trying not to think. Zazen is just sitting with awareness and natural thought. How do we remain alert and prevent abstraction?

I have also been trying to be aware of each natural thought as it arises. However:

to think about x is to attend to x;
to be aware of a thought is to attend to the thought;
thus, I have been trying to attend to the attention to x.

I can become aware that I have been attending to x but, at the moment when the natural thought arises, I am attending only to x. Zazen is becoming aware.