I'm a Roman Catholic so obviously I'm used to the use of imagery in prayer. (Yes, I'm aware it's not patristic, don't scold me.)
I'm a bit confused, in Orthodox prayer are no mental images to be used ever or is it with specific types of prayer such as the Jesus prayer? Since iconography is a very important part of Orthodox prayer (and RC, but ours are just three dimensional.

), does this mean use of physical imagery is acceptable but nothing mental? Wouldn't you need your imagination to write hymns and poems? I'm a bit loss, please help this Latin.
