Each individual soul is unique and special in terms of its essence, its capacity, and what is demanded of it.
No two souls coincide in their actions, their functions, and their paths.
No one soul can take the place of another, and even the greatest of the great cannot fill the special role, the particular place, of another that may be the smallest of the small.
From this notion, incidentally, derives Judaism's profound respect for human life.
The life of a person is something that has no possible substitute or exchange.
Nothing and no one can take its place.
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose by Rabbi Adin Steinsaltz