Moreover, how does Plato account for adding new living souls to the human population?

I'm sure your text materials address this question. Failing that, read lots:

http://www.bing.com/search?q=how+does+Plato+account+for+adding+new+living+souls+to+the+human+population%3F&FORM=EDGNNC

It actually dose not but thanks for not helping me

I actually I had did that way before coming to this website so you are late, and two I know how to look up a question up on a search engine.

Plato's account of adding new living souls to the human population can be understood through his theory of eternal Forms and the concept of the "World Soul." According to Plato, all souls exist in a timeless realm of Forms before entering the physical world.

In Plato's worldview, the physical world is a mere reflection or imperfect copy of the ideal world of Forms. The World Soul is a divine entity that animates and organizes the physical universe, including individual souls. Plato believed that the World Soul possesses all possible forms or archetypes, which are then imprinted onto individual souls before they enter into human bodies.

When it comes to adding new souls to the human population, Plato's explanation lies in the metaphysical realm. He suggests that these souls, already existing in the realm of Forms, are joined with physical bodies at the moment of birth. The exact mechanism by which this union occurs is not explicitly detailed in Plato's writings.

This concept of pre-existing souls aligns with Plato's broader philosophy of the immortality of the soul and the idea that souls reincarnate over multiple lifetimes. According to Plato, the process of souls entering new bodies is guided by a divine intelligence, ensuring that each individual is born with a specific soul that corresponds to their inherent qualities or characteristics.

It's important to note that Plato's account of adding new souls to the human population is based on speculative metaphysical ideas and is not supported by empirical evidence. As such, it is viewed as a philosophical proposition and subject to individual interpretation and belief.