"the past a worshipped stillness, ..." - ah, here we go again - "... a forgotten pain" - see, I told you so! In this poem the reader's asked to imagine this, to view it as something locked away after childhood, caged while one's attention is distracted. The concept of "colour" figures here again. This time "Color makes things move./ Trapezistes and kingfishers move. Cages don’t". Nowadays imagination has a safety net - so safe it's routinely used at the end of the act.