600,000 souls are parts of a single soul created by the Creator. This single created being was divided into parts which we call "600,000" souls. However, this number does not indicate quantity, but rather the quality of the connection between them.
When the Creator gives rise to the desire to receive pleasure, everything is a single whole; the Creator, the vessel, and the Light are like one. But in this state, both the desire and the Light sense neither separation nor connection; they don’t feel whether the creature exists or not. There is a complete absence of any sensation because any sensation in the creature can be detected only through the opposition between the creature itself and what it feels.
For that, it is necessary to distinguish between the Light and the vessel and to feel their complete oppositeness and connection. However, when the vessel and Light connect, their difference doesn’t vanish since love emerges above hatred.
Both qualities have to emerge. The distance between hatred and love, darkness and light (hatred is revealed as darkness and love as light), gives the creature the sensation of its existence and understanding of where it exists and with whom it is connected. This is the reason why the World of Infinity is not enough to outline the creature and make it independent.
Only after the creature goes through the entire process of its development, meaning that it starts at the first stage, descends to the second, and then rises back to the third, does it begin to understand what the first state was about. The created being becomes independent and similar to the Creator. That’s why it is called Adam.
In the beginning (Stage 1), the creature was just a drop of semen. Then, it realizes that the breaking has occurred and corrects it. By doing so, the creature attains perfection. It is not considered a drop of semen any more, but rather, it has the power of 600,000 souls and represents one, big, autonomous soul.
“Six hundred thousand” stands for six Sefirot of Zeir Anpin multiplied by ten Sefirot in each of them and then by ten thousand, the power of the ascent of Zeir Anpin to Arich Anpin which governs all corrections. 60 x 10,000 = 600,000. Hence, the common soul (the general, final, corrected state) is called 600,000 souls.
From the 4th part of the Daily Kabbalah Lesson 9/26/10, "600,000 Souls"