When you do Zazen, you can be in two mental states

State 1 : Lost/Getting-Caught-Up in Thoughts
State 2: A state of not being in the above State (i.e., Aware/In-the-present-moment/Not-Caught-up)

You don't need any instruction when you are in the first state, because there is nothing you can do there.

When you are in the second state, this is when you are in control and can do Zazen wrong. You can regret getting caught up, You can philosophize about how to do Zazen right, You can worry about whether your Zazen is going fine or not etc...

So what is the instruction when we are in State 2. Is it best to just sit calm and let the next thought take over you? In meditation practices where there is an object it is easy as we just go back to the object (Say breath or mantra etc...).

Uchiyama Roshi talks about bringing attention back to "Posture". Nishijima Roshi also talks about similar thing about "Keeping Spine Straight". The only problem I have with these is that there is an object there.

Isn't it much simpler and much more shikantaza like, if we didn't bring attention back to either posture or "keeping spine straight"? I am reading "Opening your hand of thought" and am a bit confused by the suggestion to bring attention back to posture. When I realize I am caught up in thought stream, my awareness is already back to the present moment. Won't it be fine if I just did nothing and sat calm, allowing the next thought (or getting caught up in next thought) to take over? Isn't bringing the attention back to posture one more additional step along the way?

what do you recommend as an instruction for the State where you are not Caught-Up? Thanks