I propose as a subject of discussion my PDF-PowerPoint "Aspects of psychic illness in Plato". I used this PDF-PowerPoint on 20th June 2024 for the lecture held at the 32nd International Conference “The Universe of Platonic Thought”, 20–21 June 2024, St Petersburg, Russia. In my study, I examine aspects of Plato’s description of the healthy and unhealthy conditions of the soul. My inquiry is mainly directed to Plato’s illustration of the progressive degeneration of the soul up to the explosion of mental illness and criminal actions. Throughout my investigation, I point out that the origin and the cause of the unhealthy and healthy conditions of the soul lie in the components of the soul. Due to its components, the soul can both reach a morally healthy condition, on the one hand, and degenerate, on the other hand. The components of the soul are given, but the development of the parts of the soul is not given: the part of the soul which prevails organises the whole soul. Individual actions are a consequence of the disposition of the individual’s soul. The possibility of being evil and of falling into a state of criminal madness is directly rooted in one of the components of the soul. The structure of the society depends on the tendency of development of the souls of the individuals living in the society and, vice versa, the development of the individual soul depends on the organisation of the society: the development of the society and the development of the individual soul steadily influence each other. The text of Plato on which I concentrate my attention is the Republic. Keywords: Illness, health, soul, Republic, society, individual, constitution, degeneration