In MCTB (Mastering the Core Teachings of the Buddha), Daniel Ingram describes the following exercise.
I sit quietly in a quiet place, close my eyes, put one hand on each knee, and concentrate just on my two index fingers. Basic dharma theory tells me that it is definitely not possible to perceive both fingers simultaneously, so with this knowledge I try to see in each instant which one of the two finger’s physical sensations are being perceived. Once the mind has sped up a bit and yet become more stable, I try to perceive the arising and passing of each of these sensations. I may do this for half an hour or an hour, just staying with the sensations in my two fingers and perceiving when each sensation is and isn’t there.
What I found most curious about this, was the assumption that "it is definitely not possible to perceive both fingers simultaneously" and that this assumption is supported by "basic dharma theory".
I understand that sensations arise and pass, but I feel like I have experienced multiple sensations simultaneously and/or the sensations of multiple body parts have formed a single sensation. I'd like to hear other people's thoughts on this.
In the form of specific questions: I can feel tingling in all of my fingers simultaneously. Does this refute his assertion that "it is definitely not possible to perceive both fingers simultaneously"? Or am I not understanding something? I suspect the latter and am hoping to be enlightened. I'm also curious what "dharma theory" he is most likely referencing? Thanks in advance for any response.