Simmias is a character from the philosophical dialogues of Plato, particularly known for his role in the dialogue called Phaedo. He is a young Theban philosopher and a student of Socrates, who engages in discussions about the nature of the soul and its immortality. Simmias presents arguments that challenge the views of other characters, contributing to the exploration of philosophical ideas. In the dialogue, Simmias uses the analogy of a harmony to describe the relationship between the body and the soul. He suggests that just as harmony depends on the strings of a musical instrument, the soul depends on the body. This metaphor raises important questions about the essence of existence and the afterlife.