I can't seem to reconcile the two ideas that Vipassana meditation involves both concentrating completely on the breath while at the same time observing bodily sensations. Aren't these two mutually exclusive? How can one concentrate on the breath while being open to new sensations?
Vipassana does not involve concentrating solely on the breath. Instead (one form of) it involves resting your attention on the breath. While keeping your attention on your breath your awareness naturally has to be open to unconsciously "decide" whether or not the attention should change to something else, so already it is naturally open in this situation. By placing your attention on your chosen object of meditation you are implicitly opening your awareness.
At first it's not obvious: you may feel that you are really forcing your attention onto your breath at the expense of other sensations, but as you relax and open further you will begin to perceive your awareness with much more clarity.
Source: The Mind Illuminated
If you simply observe everything, eventually, the mind starts wandering.
So, observation of the breath in vipassana serves a few functions:
- It anchors the mind into the task of observing the breath and you need mindfulness to keep returning to this task, to prevent the mind from wandering.
- It calms the mind down.
- With the breath, there comes other physical sensations that are observable, like the movement of the abdomen, movement of air through the nasal passage etc.
- With the breath, there are related mental states that can be observed like calming down, agitated, unhappy, happy etc. because negative mental states tend to cause heavy agitated breath and positive mental states have lighter breath.
- The relationship or mutual influence between mind and body can be observed.