In geniuses on, Plato on the soul refers to the collected ideas, theories, and beliefs of Plato on the concept of the soul, e.g. soul mate.

Overview
In c.1617, Lucilio Vanini, in dialogue style, was referring to Plato’s views on the soul as follows: [1]

Plato has maintained the immortality of the soul against many philosophers. It is true, replies the other, but he has likewise held for the immortality of the soul of that little bird you see in that cage.”

(add)

Quotes | On
The following are quotes on Plato’s soul theories:

Plato believed in an immortal soul (compare: mortal soul) capable of surviving the death of the body. He wrote about it in Phaedo and The Republic, two of his many influential dialogues. Like most thinkers that followed in his footsteps, Plato believed that the soul is the principle that gives life to the body. For the great philosopher, the soul was a life soul, and it became a surviving soul after a person’s death. Plato’s doctrine maintained that the soul originated in the realm of the dead, temporarily passing through the world of the living, before it returned to the underworld in and endless cycle of reincarnation. Plato was one of he early dualists for whom the soul was a separate substance, distinct from the body, and capable of existing on its own. Plato also theorized about the structure of the soul and proposed that it is composed of three parts: the appetitive, the spirited, and the rational. The appetitive soul was the lower of the three, the one responsible for our basic desires such as hunger, thirst, and sexual drive. On top of the hierarchy sat the rational soul, the principle that gives us our quintessentially human capacity for thought and reason. In the middle we find the spirited soul playing the role of a mediator between the appetitive and the rational soul. Plato even located the three parts of the soul in different areas of the body. The rational soul had its place in the head, the spirited in the heart, and the appetitive in the belly.”
Julien Musolino (2015), The Soul Fallacy [2]

See also
Geniuses on the soul

References
1. Durand, David. (1714). The Life of Lucilio (alias Julius Caesar) Vanini: Burnt for Atheism at Toulouse with an abstract of his writings being the sum of the atheistical doctrine taken from Plato, Aristotle, Averroes, Cardano and Pomponazzius's philosophy with a confutation of the same; and Mr. Bayle's arguments in behalf of Vanini completely answered (Amz) (pg. 76). Publisher, 1730.
2. Musolino, Julien. (2015). The Soul Fallacy: What Science Shows We Gain from Letting Go of Our Soul Beliefs (foreword: Victor Stenger) (pg. 44). Prometheus.

Further reading
● Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (Plato, pgs. 14-15). HarperOne.

External links
Plato’s Theories of Soul – Stanford Encyclopedia of Philosophy.

TDics icon ns