We use the zero imposition when we talk about a word's properties other than its meaning.
Egs. "'Cute' has four letters," "'Cute' is monosyllabic."
Sister Miriam Joseph describes the zero imposition "like a window or like eyeglasses at which we look instead of through..."
We use the first imposition when we use a word only in relation to its meaning. The first imposition is the most commonly used by a wide margin. Every word in this and the previous two sentences are being used in the first imposition.
Egs. "I think the kitten is cute," "You have a cute smile."
Sister Miriam Joseph describes the first imposition "like a window or like eyeglasses through which we see objects but of which we are unaware."
We use the second imposition when we refer to the properties of a word that only its meaning can reveal.
Egs. "'Cute' is an adjective." "'Cute' is the predicate of 'my new kitten is being.'"
If Sister Miriam Joseph had described the second imposition, she might have said it was like looking at one's eyeglasses and through them AT THE SAME TIME.
No way, 'I' is to 'who' as 'me' is to 'whom'