The first verse of this poem is an example of the use of quiddity as it describes the “thusness” and “no otherness” of the world.In the second verse the poet shows how we can see through this world into something beyond it.He shows the transparency of the world even as we concentrate on perceiving what is.As the poet was a Catholic priest he has written it from a Christian view of Christ and God but the essential meaning can refer to any religious view point or even to a non religious one as it can be interpreted metaphorically.Indeed itis already metaphorical
As kingfishers catch fire, dragonflies draw flame;
As tumbled over rim in roundy wells
Stones ring; like each tucked string tells, each hung bell’s
Bow swung finds tongue to fling out broad its name;
Each mortal thing does one thing and the same:
Deals out that being indoors each one dwells;
Selves — goes itself; myself it speaks and spells,
Crying What I dó is me: for that I came.
I say móre: the just man justices;
Keeps grace: thát keeps all his goings graces;
Acts in God’s eye what in God’s eye he is —
Chríst — for Christ plays in ten thousand places,
Lovely in limbs, and lovely in eyes not his
To the Father through the features of men’s faces.
How my heart sings 
A favourite of mine too. I love the imagery of the opening lines – sound and colour (reminds me of Janet’s Humming Birds) – and the wonderfully concise “Crying What I dó is me: for that I came.”
I was fortunate to do this for O level where we did a “modern” course.Without that I’d not have read so much poetry afterwards.And I came across the word quiddity in a novel by A S Byatt some years back but never heard it spoken.I see that many people read these word posts so a desire for learning is strong in many adults.