Rabbi Adin Steinsaltz writes:
Western culture places so much value on culture that it calls it “spiritual life.”
Why should an individual’s brain be more sacred than his body?
Spirit and matter are two forms of life, two different modes of the same reality.
I would say that Judaism anticipated somewhat the theory of relativity.
Before Einstein, matter and energy were thought to be two entirely different entities.
We know today that they are basically the same and are simply two facets of the same reality.
Similarly, there is a conventional distinction between mind and matter.
Judaism has always refused to accept this division.
Mind and matter are only two phases of the same reality.
One cannot be associated with good and the other with evil.
In Judaism, the real opposition is not between mind and body, or body and soul, but between the sacred and the profane.
And it is clear that many facets of “spiritual” life are unrelated to the sacred.
Only the sacred and the profane are two different worlds.
In contrast, the differences between the various facets of existence, both material and spiritual, are only quantitative.
This is why we can be totally absorbed in the “spiritual” life of the mind-for example, devoting our life to philosophy or music-and nevertheless live completely in a nonsacred world.
Hasidism emphasizes the close connections between thought and matter.
Thought is the outcome of the functioning of a physical organ, the brain.
This is why thought is one thing, and the soul, another.
–Rabbi Adin Steinsaltz