What are human beings meant to eat? How does Tanakh envision an ideal human diet, and what implications-if any-should that biblical ideal have for the present?
At the end of Genesis 1, God tells newly created human beings what they are to eat: "See, I give you every seed-bearing plant that is upon all the earth, and every tree that has seed-bearing fruit; they shall be yours for food" (Genesis 1:29). Next, God announces what the animals will consume: "And to all the animals on land, to all the birds of the sky, and to everything that creeps on earth, in which there is the breath of life, [I give] all the green plants for food" (1:30). Whatever the fine distinctions between what humans and animals may eat, at first both are assigned a vegetarian diet. Or as Jeremy Benstein memorably puts it, in the biblical creation story "humans and animals were on the same side of the knife and fork (and tooth and claw)."
It is only after the flood that the relationship between human beings and animals changes - and rather dramatically, at that. When Noah finally emerges from the ark, God declares to him and his sons that "every creature that lives shall be yours to eat; as with the green grasses, I give you all these" (9:3). Where before humans and animals alike had sustained themselves by eating vegetation, now animals are given over to be consumed by people. The permission given to humanity here is a departure from the ideal established by God at the time of creation. Many Bible scholars assume that humanity's new diet represents a "concession to human need for aggression." Others suggest that in the aftermath of the devastation wrought by the flood, Noah and his sons were understandably anxious about starving. As R. Isaac Abravanel (1437-1508) explains, seeing the devastation wrought by the deluge, the survivors of the flood worry about dying of starvation. Taking note of their fears, God effectively answers, says Abravanel, "If there is no fruit for you to eat, take from the animals for your food."
Whatever God's rationale, one thing seems clear: "Human exploitation of animal life is here set within the context of a post-Flood, deteriorated situation. It is radically different from the ideal of Genesis 1." As if to remind humanity of this far-from-ideal situation, God imposes a crucial limitation: "You must not, however, eat flesh with its life-blood in it" (9:4). Consumption of meat is now permitted, the Torah seems to be saying, but "wanton consumption of meat" is not. Bible scholar Moshe David (Umberto) Cassuto (1883-1951) explains that the prohibition on eating blood serves as a reminder of God's ideal in a time when a compromise has become necessary. "Apparently, the Torah seeks to convey that in principle man should refrain from eating meat," Cassuto notes. The prohibition on blood "implies respect for the principle of life ('for the blood is the life'), and it serves also... to remind us that rightly all parts of the flesh should have been forbidden. It behooves us, therefore, to eschew eating at least one element thereof in order to remember the earlier prohibition." Permitted to eat meat, human beings are forbidden to forget that this permission is a concession, a far cry from God's optimal picture of reality.
But the Bible is not content to leave the vegetarian ideal in the antediluvian past. The prophet Isaiah imagines a radically transformed messianic future in which the world has been brought to an unprecedented state of tranquility. In the future Isaiah pictures, human nations will not do violence to one another: "Nation shall not lift up sword against nation, and they shall never again know war" (Isaiah 2:4). Nor, crucially, will animals prey on those weaker than they: "The wolf shall dwell with the lamb, the leopard lie down with the kid; the calf, the beast of prey, and the fatling together, with a little boy to herd them. The cow and the bear shall graze, their young shall lie down together; and the lion, like the ox, shall eat straw" (11:6-7). Human-human relations will be healed, as will animal-animal relations. Although Isaiah does not say so explicitly, it does not seem too much of a stretch to imagine, as Abravanel does, that human-animal relations will also be healed. In the future, then, human beings, like lions, will cease to eat meat. This is part of the logic of overcoming predation.
But what significance, if any, should these messianic notions have for present-day life - are eschatological visions intended to have contemporary ramifications? Does our picture of the messianic age make a claim on us now, in our far-from-messianic, painfully unredeemed world? Are we meant to wait more or less passively for the messiah to transform our reality, or are we asked in whatever small ways we can to anticipate the messianic future now?
R. Joseph Soloveitchik argues that according to Jewish theology, human beings are called upon to be creators. Just as God creates worlds, so should we. R. Soloveitchik writes that "Halakhic man discerns in every divine pledge man's obligation to bring about its fulfillment, in every promise a specific norm, in every eschatological vision an everlasting commandment (the commandment to participate in the realization of the prophecy)."  Soloveitchik says this is as if were obvious, even self-explanatory. But it is in fact quite a radical statement: When God makes a promise about the messianic future, implicit in that promise is a human obligation to help bring that future about. Many traditional religious thinkers insist that the opposite is the case - a divine promise is just that, a promise made by God, to be fulfilled by God and God alone. For a human being to try and bring God's eschatological promises to fruition would usurp a prerogative that is exclusively God's. Satmar anti-Zionism, for example, is based on just this understanding of the human (non-)role in bringing about a redeemed future. Soloveitchik's words open a door for those who feel they should anticipate Isaiah's non-violent future now. By refusing to take animal life for the sake of food, they would be taking a small step towards what Soloveitchik calls "the realization of [Isaiah's] prophecy." Actually, this argument could be even stronger: Soloveitchik does not talk about permission to assist in the messianic unfolding; he talks, rather, about an obligation to participate in that process. Thus, if you accept Soloveitchik's premises, you might hold that vegetarianism unequivocally becomes a norm even in the present.
And yet the Bible's vision of Jewish eating in the present is about kashrut, not vegetarianism. Parashat Shemini presents lengthy lists of land-animals, sea-animals, and birds that may or may not be eaten. Eating chicken but refraining from vulture has nothing to do with Isaiah's vegetarian ideal... or does it?
Almost all species in the list of prohibited birds in parashat Shemini are birds of prey (11:13-19). Bible scholar Baruch Levine suggests the rationale behind this prohibition: Such birds "feed on carrion and tear the flesh of other living creatures in their pursuit of food. As such they [are] considered unfit as food for a people forbidden to eat blood and commanded to avoid flesh that had been torn by living creatures."  By contrast, birds permitted for consumption - hens, doves, and pigeons, for example - feed on grain. Levine notes more expansively that in general, the animals the Torah permits are herbivorous. Why may Israelites not eat predators? Levine explains: "Ideally, humankind should be sustained by the produce of the earth. When, instead, other living creatures are used as food, as is permitted, such use should be restricted to living creatures that sustain themselves with what grows on the earth and that do not prey on other living creatures or attack man."
On this account, much as Cassuto contends that the prohibition on consuming blood is intended to recall the total prohibition on consuming animals at all, so also the biblical laws of kashrut call to mind the primordial and ideal prohibition. Bible scholar Gary Rendsburg amplifies Levine's interpretation: "Humans are unable to live up to the vegetarian ideal set forth at creation; God compromises and allows humanity to eat meat. But Israel wishes to adhere to that ideal, even in compromised fashion, and therefore Israel consumes only those animals that themselves have not killed other animals." Or, to put the matter somewhat differently, the Torah projects its ideal human pattern for living and eating onto the animals: "Israel clearly stressed the vegetarian ideal, and while it could not uphold the ideal, it transfers that ideal onto the animal kingdom, permitting [only] herbivorous animals to be eaten. These animals... remind the Israelites of who they are or at least of who they should aspire to be in an ideal world."
If this interpretation of Leviticus 11 is correct, then perhaps one can argue that to limit oneself to a vegetarian diet for religious reasons is, roughly, an instance of lifnim mishurat hadin, of doing more than the law actually requires in following its underlying spirit.
Taking Tanakh seriously, we are obligated to remember that permission to eat meat is a concession, a far cry from the Torah's ideal. However one answers the somewhat theoretical questions I have raised - whether in an ideal world, Jews would refrain from eating meat; and whether in light of that ideal, some Jews, at least, ought to do so now - this fact ought to remind us of our responsibility to consume meat in the most humane way possible, a responsibility of which we all too often fall appallingly short.
 Jeremy Benstein, The Way into Judaism and the Environment (2008), p. 45.
 Tamara Cohn Eskenazi, Torah: A Women's Commentary (2008), p. 44.
 R. Isaac Abravanel, Comments to Genesis 9;1ff. Cf., in a similar vein, Terence E. Fretheim, "The Book of Genesis: Introduction, Commentary, and Reflections," in The New Interpreter's Bible, vol. 1 (1994), p. 399. Of course, the second explanation invites the question of why permission to eat meat was not time-limited. Abravanel implicitly tries to address this question, I think, in suggesting that in giving Israel manna in the desert, God was trying to return the people to a vegetarian diet. See Abravanel to Exodus 16:4.
 Victor P. Hamilton, The Book of Genesis 1-17 (1990), p. 314.
 Gary A. Rendsburg, "The Vegetarian Ideal in the Bible," in L. J. Greenspoon, R. A. Simkins, and G. Shapiro, eds., Food and Judaism (2005), pp. 319-33. Citation is from p. 323.
 Moshe David Cassuto, A Commentary on the Book of Genesis, pt. 1: From Adam to Noah (trans. Israel Abrahams) (1961), pp. 58-59.
 This is the implicit logic of Abravanel's comments to Exodus 16:4. This is also the assumption of Cassuto, Commentary on Genesis, p. 59.
 I am grateful to Prof. Gary Rendsburg for our exchange on this point. I would add that the logic here is more compelling if one assumes that Isaiah's description of the animal future is intended as a realistic picture rather than a metaphor for a peaceful human future. Compare, for example, Maimonides (1135-1204), Mishneh Torah, Laws of Kings, 12:1, who insists that the images in Isaiah 11 are metaphors, with Saadia Gaon (882-942), The Book of Beliefs and Opinions, Treatise 8 (Rosenblatt edition, pp. 318-319), who affirms that the future world will be fundamentally transformed. Among modern academic scholars, compare John Oswalt, Isaiah (2003), p. 283 ('figurative"), with Walter Brueggemann, Isaiah 1-39 (1998), pp. 102-103 ("deep, radical, limitless transformation").
 Joseph B. Soloveitchik, Halakhic Man (English translation, 1984), p. 100. I am interested here not in whether R. Soloveitchik would be sympathetic to this potential application of his thinking but in what the logic of his position makes possible.
 Baruch A. Levine, Leviticus (1989), p. 246. Cf. also Mishnah Hullin 3:6.
 Levine, Leviticus, p. 248.
 Rendsburg. "Vegetarian Ideal," pp. 327-328. The more commonly accepted scholarly interpretation of the kashrut rules in Leviticus is anthropologist Mary Douglas' suggestion that for the Torah, pure animals are those that "conform fully to their class," while impure animals are those that are "imperfect members of their class"-that is, those that defy clear and easy classification, Mary Douglas, "The Abominations of Leviticus," in Purity and Danger (1966), pp. 41-57. I find the broad contours (if not always the smaller details) of Douglas' approach compelling, so much so that I suspect the Levine-Rendsburg interpretation will gain more traction if it is seen as complementary to Douglas' approach rather than representing an alternative to it. Both Levine and Rendsburg appear to think the two approaches can be integrated.