Physical desire, whether for the good or otherwise, is at first grasped by man as the desire of his very self.
Only afterward is there room for discrimination: What do I really want? What is merely a reflex action and what is an inner need?
All these are matters for investigation and discussion.
They issue from the fact that the body and the soul grow together out of the one cradle, and for a long time, the soul does not know the world or itself except through the instruments of its physical shell.
If we may use an old, not so agreeable image, we may picture the metempsychosis or passage of the soul through animal and human forms, until the soul learns that it does not have to function according to the pattern of an animal.
Man is brought up in terms of animal selfhood because the human body, no matter how developed, is that of an animal–which also explains man's limitations, incidentally, even the restrictions of his intellectual qualities.
In order to discover the fact that he is a human being, something of an entirely different essence, he has to separate the vessel from its contents, and he has to learn to see the world with other eyes, not through his ordinary implements of vision.
Therefore, it is said that the soul has first to overcome physical matter, to overcome it in the same sense of overcoming the first level of life, where matter rules supreme.
Afterward, it is not enough that the soul becomes stronger–the physical nature has to be subjugated and used.
For the soul, no matter how liberated it is, has to function physically through the body and has to think through the physical brain.
Not only the body as such, but even the brain, or the mind, has to be transformed into an instrument.
–Rabbi Adin Steinsaltz
From The Sustaining Utterance by Rabbi Adin Steinsaltz