Mindfulness "in" or "at" the present moment

I am currently assisting in editing a series of talks by Bhante Khippapanno for publication.  In the talks,    Bhante repeatedly refers to being mindful "at the present moment" rather than with the more commonly used phrase, "in the present moment."  What difference does a preposition make?

The prepositions "in" and "at" can be used as prepositions of place or of time. As prepositions of place, "in" implies an enclosed space, whereas the preposition "at" implies reference to a position.  As prepositions of time, these prepositions are distinct in terms of the duration of time involved.  The preposition "in" is usually used for longer stretches such as days, weeks, months and so on;  whereas "at" is used with respect to a precise time.

Mindfulness always has an object of which it is mindful, and it arises as a mental factor accompanying wholesome mental states (e.g., a moment of kindness or generosity) or may arise after the passing away of an unwholesome mental state.  I am mindful of anger at the present moment, but I am not mindfully angry.  When I was angry, just a moment ago, I was not mindful since the anger and mindfulness are incompatible.  Strictly speaking, the mindfulness of anger is "present" only when the anger has passed away.

The preposition "in" in the phrase, "mindful in the present moment," is inappropriate in two ways.  While the spatial sense of the preposition is only metaphorical,  it suggests that mindfulness is enclosed in a space that includes its object, which certainly cannot be the case when the object is an unwholesome mental state.  In the temporal sense, it implies that the present moment is of much longer duration than it could be in terms of mind moments, which are extremely brief.

The preposition "at" in the phrase "mindful at the present moment," on the other hand, is appropriate both in spatial and temporal terms.  Again, the spatial sense is metaphorical, but it is appropriate since it implies a position with respect to the object of mindfulness.  In the case of a wholesome mental state, the position of mindfulness is together with, that is, concurrent with or simultaneous with the object; in the case of an unwholesome mental state, the position of mindfulness is next to the unwholesome object, that is, it can arise in a succeeding moment. In the temporal sense, "at" captures the precision of the timing involved with the extremely brief mind moments in which mindfulness and its object arise.