how does the church tie into the novel?

Children as subhuman

Several times in the novel, children are referred to as subhuman, almost human, or not quite human. This notion, allegedly espoused by the Church at the time (Father Terrier mentions it to Jeanne Bussie), seems to have its roots in the idea that very young children do not have free will--particularly in choosing to obey or disobey God. It was not only that children did not have the rights of adults and adults thus had responsibilities toward them. Although children were protected by law from being murdered (such as Grenouille's escape from infanticide), and they were provided for up to a point by the state and the church (in establishments like Madame Gaillard's), they were not considered full human beings like adults were. This lower view of children can be seen in the treatment of apprentices, who were children as young as eight (or younger) used in a fashion similar to domestic animals.

Another reason for treating children as less than human was the likelihood of death in infancy or childhood during the Ancien Regime. It may have seemed unwise to invest too heavily in beings who were so likely to die quickly. Orphans like Grenouille were the most extreme example of so-called subhuman children, since they had no family to love them. This rejection of what one might call equal rights for children, held by many people around Grenouille in his childhood, undoubtedly contributed to his later psychosis.