Everything depends upon the calculation, the decision that was accepted from the start. A human differs from an animal in that he has a Rosh with which he decides how much Light he can receive in order to bestow. The desires with which I receive are called the Toch of the spiritual Partzuf (the body). And where I cannot receive is called the Sof (the end).
What follows from this is that through this decision I divide my reality and all of me into three parts. The part in which I receive a decision is the Rosh (head), and it is the most important part of me, thanks to which I am called man and am different from an animal.
An animal has only a desire without a division into a head, torso, and ending. This means that it is dominated by the direct Light that influences it and it responds accordingly. Between these influences, in the middle, there is no head; there is no restriction.
This is why an animal is absolutely linked to the Creator instinctively. An animal doesn’t make mistakes, but always carries out the commands of the Creator. Therefore angels belong to the animal level.
But man takes account of how to resemble the Creator, and so he makes mistakes. He has a head by which he becomes independent! And so he doesn’t use all of his desire, but divides it into parts and constructs a spiritual Partzuf.
In the beginning we have only a desire and we carry out a restriction on it. In this manner we receive the possibility of considering what else to do with our desire; we are working with the head.
Work in the head against the desire, not according to its wishes but according to my calculation, is called a Masach (screen). This means that the screen is desire + restriction + decision to resemble the Creator, and my goal is built from the head and intention.
We must bring all of these concepts as close to ourselves as possible because we are already in them. We only need to clarify where the head is, where the screen is, where the restriction is, where the intention is, how do I receive, and how do I divide the desire from here to there.
It is as if I am on a diet and choose the dish that will bring me what and how much I am allowed to eat and what I am not. We make a calculation like this with the head of the Partzuf, and after that we realize this decision in the body. It’s all very clear, the only question is for whom am I doing this?
This is the only question, the entire difference between the physical and the spiritual is in that. In the physical world we maintain a diet in order to look beautiful and to be healthy. Whereas, in the spiritual world we do this with a different intention: with a hope that we are giving contentment to the Creator.
From the 4th part of the Daily Kabbalah Lesson 4/23/14, Writings of Baal HaSulam