Over on Tablet, David Goldman explains how the Orthodox Jewish theologian Michael Wyschogrod taught him the biblical reasons behind the dietary laws :
Rational argument about kashrut falls short, but I was ready to hear a biblical argument, especially now that my daughter had called me on the carpet. And so we read Wyschogrods commentary together. Christians saw the serpent in the Garden of Eden as Satan, he began, but that never occurred to the rabbis of antiquity. The snake was only the cleverest animal of the many God made to try to keep man company, for, as it says in Genesis 2, it is not good for man to be alone. But for Adam no fitting helper was found. And then God made Eve. Only woman is the proper companion of man, Wyschogrod argued, but animals are also companions although less than fully satisfactory ones.
What does that have to do with eating animals? my daughter interrupted. That was where Wyschogrod was heading. Genesis tells us that even if the animals are not as close to God as are we, neither are they so far from him. The Torah is the first document in history to evince concern for the welfare as well as the sentiments of animals; domestic animals must rest on the Sabbath, and an ox must be allowed to eat the grain that it threshes. To kill and eat them is a grave matter; we have no rational calculus by which to weigh the human requirement for nutrition against the trace of the divine in animal life. That is why Jews may consume meat only with supernatural sanction, under restrictions imposed by God himself. God, Wyschogrod offers as an afterthought, probably would prefer us to be vegetarians.