Written by St Anselm of Canterbury, Proslogium (sometimes referred to as Proslogion) is the Saint’s written discourse on god and his qualities.
Considered one of the first written works of theology that discusses the possibilities of god in depth, this text is an interesting look into religion and religious thoughts of the past. Much detail goes into the possibilities that god may have, such opposing qualities include god’s power and omniscience.
There’s two version of this piece I would recommend. Forgotten Books offers up an edition that’s quite interesting. It is the original text, but saying that is an understatement. A good amount of time has been taken to make the translation as close to the original as possible in modern English. The original text has been digitally copied and the format and texture of the pages are here as they were from the beginning (with slight digital repairs to allow it to be read at ease of course). It’s really interesting to own this copy, as it feels like an actual ancient text when you flip it open. The other option is the Open Court edition. Translated into modern English and with a second edition in ’98, this copy is the better of the two for those interested in the scholarly side. It includes the main text, but also includes some argument in the discourse which helps context and better understand Anselm’s own stance on the ideas.