We all used to be one soul that split into a multitude of egoistic parts. What does that mean? How to return to the initial state? And what force returns broken pieces to the initial state?
In my opinion, there is indeed only one soul in the world, as it is written (Genesis, 2:7), “and breathed into his nostrils the breath of life.” The same soul exists in all the children of Israel, complete in each and every one, as in Adam ha Rishon since the spiritual is indivisible and cannot be cut—which is rather a trait of corporeal things.
Yet, saying that there are 600,000 souls and sparks of souls appears as though it is divided by the force of the body of each person. In other words, first, the body divides and completely denies him of the radiance of the soul, and by the force of the Torah and the commandments, the body is purified, and to the extent of its purification, the collective soul shines upon him.
(Baal HaSulam, Fruit of the Wise, “600,000 Souls”)