The word Quiddity means the essential nature of a thing. Herbert is not talking here of the church, but poetry.
OED Word of the Day: quiddity, n. The inherent nature or essence of a person or thing; what makes a thing what it is hhttp://bit.ly/2srCbWA
— The OED (@OED) January 17, 2019
And he reflects that by the issues of gentle life in his time, poetry is not that useful. But it is who he is, and it is given in service to God.
>MY God, a verse is not a crown,
No point of honour, or gay suit,
No hawk, or banquet, or renown,
Nor a good sword, nor yet a lute:
>It cannot vault, or dance, or play;
It never was in France or Spain;
Nor can it entertain the day
With my great stable or demain:
>It is no office, art, or news,
Nor the Exchange, or busie Hall;
But it is that which while I use
I am with thee, and Most take all.
>George Herbert, 1633