Arthur and Waldo Brown

Patrick White's The Solid Mandala has two main characters. They are the brothers Arthur and Waldo Brown—two aspects of the same person, much like a mandala (two-sided but still one). 

Arthur is the "good" brother, or the one likely to appeal to the reader. He is who we sympathize with. He is sincere and modest. He has an intellectual disability and his disposition is friendly. But White also shows him as part of the archetype of the "noble primitive": one who is inherently good because he is apart from civilization. Many others regard him as strange or to be looked down upon—even to be feared. Even still, he proves himself more capable of forging relationships than his brother. His intellect is much more intuitive and emotional than Waldo’s. Arthur finds great meaning in his collection of marbles, specifically the titular solid mandala. 

Waldo is very conformist. He is outwardly unemotional and lives within books and papers, yet he is also self-doubting and filled with inner turmoil. Waldo neither believes nor understands how he and his brother are tied together. He resents Arthur through the years for his successes, feeling that he should have come out on top. He is infuriated that Arthur knows him so well. Waldo works in a library and attempts to write novels and poetry. He lacks the talent that Arthur has because is so lofty and intellectual: his words come across as cold and emotionless.

Arthur and Waldo are supposed to represent sides of the same coin. Arthur does seek to join with his brother, but Waldo rejects him. At one point in the story, this is made explicit when Arthur offers a mandala to Waldo, and Waldo turns it down. Yet as they grow older, they depend on each other: walking dogs together, holding hands. It is almost as if Arthur and Waldo become one “whole” person together.

Dulcie Feinstein

Dulcie Feinstein is the woman both Arthur and Waldo want to be with and both propose marriage to. Arthur's love for her is platonic but strong. Waldo's proposal is tepid and done out of a sense of obligation, believing it to be what society wants. Dulcie eventually marries someone else and has children, one of whom she names Arthur. She holds on to one of Arthur's solid mandalas. 

Mrs. Poulter

Mrs. Poulter is a devoutly religious woman who is a friend to both brothers and occasionally goes on outings with Arthur. She treats him like a son, having lost her own child, and the two spend a good amount of time together for a while. She is entrusted with one of Arthur’s solid mandalas.

Mrs. Dun

Mrs. Dun is an acquaintance who condemns the brothers as unnatural. She is a stereotypically “suburban” woman who does not treat Arthur with respect due to his different abilities.

Mr. and Mrs. Musto

Mr. and Mrs. Musto are the neighbors; Mrs. Musto is very talkative and Mr. Musto is the maker of the mandala who defines what it is for the brothers from his encyclopedias.

Wally

Wally is someone who works with Arthur but goes off to war and is killed.