In inquiry, we put the mental field to good use.
We bring attention somewhere, guided by the mental field.
And we filter content of awareness in different ways, also through the mental field.
For instance, in exploring sense fields, we use the mental field to filter out what is sensation, sound, sight, taste, smell and mental field, and we also use the mental field to guide attention to different parts of these.
This filtering itself can be investigated.
How does it happen? How is sensation filtered out from everything else? Do I find an visualized/imagined boundary in the mental field, telling me where to look? A memory of sensations from the past that I compare whatever is happening with, so I can decide what is a sensation? Does the imagined boundary look real and solid, or ephemeral and an overlay without substance? What happens if it is taken as real and solid? If it is seen as an overlay without substance?
What is attention? How is the mental field used to guide attention? Is there a visualized/imagined boundary there too, with attention brought to what is inside of it, and the rest going into the periphery?
There is doing. Can I find a doer? Who or what is observing? If I have an image of a doer or an observer, is that too in the mental field? Can I find it outside of the mental field? What is left if this doer is seen as just a creation of the mental field?