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.
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose, p. 38, by Rabbi Adin Steinsaltz