The poem centres on the theme of religious persecution and the corrupted dictates of dogmatic Church teachings.
On the other hand, a reader might theorise that Blake intends to portray the child as precocious and with intentions to dissent from Church teaching—perhaps the Priest thinks so.
Certainly Blake seems to hearken back to the time when the Church wielded almost unchecked powers throughout England (and most of Europe) to judge and destroy anyone it deemed intolerable in thought or behaviour.
The first quatrain introduces the subject of love of self in the voice of an omniscient narrator; the language is highly stylised.
The second quatrain is the much simpler speech of a little boy expressing his thoughts on love of God, of others, and of nature.