the Word "I" associated with a feeling of existence which in turn seems to be located in the chest/head
Is that true?
To start off the looking at the relationsship of sensation and thought, here a lovely excercise.
Please do it joyfully and thoroughly:
Find a quiet place and a quiet moment.
Sit or lay down and relax. Relax.
Can you attend to sensation exclusively?
Not minding thought babbling about this and that. Not minding thought giving "meaning" to sensation?
(Non-Verbal) Thought might tell that "I am lying" here or "My body is lying here" or "A body is lying here".
But could this be known from pure sensation?
(Non-Verbal) Thought might give a sense of there being "soft pressure against the back".
But does raw sensation tell anything about "soft", "pressure" or "back"?
Upon having arrived there, please pose the following questions.
While ONLY attending to sensation.
Can it be known how tall the body is?
Does the body have a specific shape, size or weight?
How many toes are there?

