[9][10] Quaque wrote a series of letters to the Society for the Propagation of the Gospel, London from 1765 to 1811 telling of his successes, trials, and hardships during his time at Cape Coast Castle.
Through his letters, particularly the one dated 1767, we get a thorough sense of the difficulty of Quaque's job as a missionary and how it conflicted with the traditionally polytheistic society he was living in.
In his letter dated July 30, 1775, he mentions the resulting bloodshed of a conflict, which he later mediated, between the local Dutch allies and his own townspeople.
Such conflicts, as well as competition with the slave trade and the American Revolution, play a large role in the number of factors behind Quaque's supposedly limited success.
Yet for these reasons, many grant Quaque glory for the number of baptisms he was able to perform, as well as the fact that he consistently stayed in touch with the Society over the course of several decades, even into his state of illness, despite the London headquarters only sending him 3 letters in response during his entire time stationed there.
On the European side, he was criticized for becoming too involved in the coastal society, largely in part due to his marriages to local women, and the interpretation of his letters to not have been dissociated from his own culture.