The argument from religion or “divine law” holds that because God made animals for human consumption, it is morally justified to eat them. These arguments usually come from followers of the classical monotheistic religions, so this response will be focused on answering the claim as argued an Abrahamic perspective, that being the perspective of mainstream Islam, Judaism and Christianity.
Within religious ethics, there are generally three categories of acts, act that are forbidden, acts that are mandated, and acts that are permissible. We must first acknowledge that almost all theologians and believers are in agreement that the consumption of animal flesh is not mandated by any Abrahamic tradition. That you must consume animal flesh is not present in the dietary laws set down by any mainstream scripture, these laws merely set out the cleanest and most permissible way to slaughter an animal. Therefore, this argument can be used as a defence for eating animals, but it certainly cannot be used as a reason people should eat animals. In the scripture of all three Abrahamic traditions, there are actually several passages which could very easily be interpreted as being in support of a vegan worldview.
In the Hadith, The Prophet Muhammad (peace be upon him) recounts a story of a prostitute giving water to a thirsty dog at a fountain, and for this act of kindness Allah forgave all of her sins. On another occasion, The Messenger of Allah said, “An ant had bitten a Prophet among the Prophets and he ordered that the colony of ants should be burnt. And Allah revealed to him, ‘Because of an ant’s bite you have burnt a community from amongst the communities which sing My glory.” It is clear then, that for Muslims, animals matter morally and how we treat them is of utmost importance to Allah. If Allah responds with fury to the killing of an ant, though it it taught that we cannot know His mind, it is not unreasonable to argue that He would have a similar response to slaughtering billions of animals per year for food. The Quran actually goes as far as to say that humans and animals are morally equal, “A good deed done to an animal is like a good deed done to a human being, while an act of cruelty to an animal is as bad as cruelty to a human being.“
In The Talmud we find equally convincing passes that attest to the equality of humans and animals, The Talmud states: “His mercies extend to all His creatures” (Psalms 145:9). In The Bible we are told that believers should “keep yourselves from blood and things strangled and from dead bodies of birds and beasts, and from all deeds of cruelty, and from all that is gotten from wrong. Do you think that the blood of beasts and birds will wash away sin? I tell you, No! Speak the the truth, be just, and merciful to one another and to all creatures, and walk humbly with your Creator“ (The Gospel of the Nazirenes, 7:10). The theme throughout all of the creation stories of all of these religions emphasis the stewardship that God expected of humans, that we were meant to look after the world and the animal’s who inhabit it, not to dominate them. The notion that animals were created solely for human use is simply not supported by scripture.
As you we can see, it is not difficult to defend a view of scripture that not only supports veganism, but actually mandates it. “Thou shalt not kill” has no “but” or “unless” tagged on the end. Truthfully, though, it is not difficult to also interpret scripture in support of killing animals for their flesh, as a traditional interpretation of any of these texts will reveal. In absence of direct word on any given issue, Muslims, Jews and Christians are quite comfortable with interpreting general principles such as the sanctity of life, and applying it to modern ethical issues like IVF and abortion. It is clear that at the very least, none of these religions mandate consuming animal flesh, even if they do permit it. Permitting an act is not the same as requiring it, and that it is permitted does not necessarily mean that it is what we should be doing.
The general principle of valuing life, all life as sacred and created by God, fairly clearly could be applied to animal rights. There is also the principle that runs through all faiths, of acting in a loving way and treating our fellow beings as we would like to be treated. Surely it is not out of the question to apply this thinking to animals, too. Even if scripture did mandate eating animals, which as we have found it does not, there are plenty of other things all three scriptures mandate that we no longer consider ethical. These texts are very much a product of their time, coloured, like all texts, by the historical and cultural baggage of the context in which they were created. Industrial farming did not exist when the prophets walked in the world, nor did intensive crop farming, or intensive breeding. So we have to look at general religious principles and apply them to these very modern problems. The prophets didn’t talk about keeping animals for flesh on a commercial scale. They did, however speak often about how all life is sacred and created by God. They did preach about taking the side of the weak against the strong, of the downtrodden and most vulnerable in the world against those who would harm them. There are few as weak and as downtrodden as the animals we raise for our food.
More fundamentally than all of this, the argument for animal consumption on the grounds of religion is weak at its very foundation. The most rational argument is the argument which makes the least assumptions; if an argument depends on the existence of a deity, regardless of whether God exists or not, that is a major flaw in any argument. Not all religious doctrine has to be rational, or even intends to be, but since this defence aims to be a rational attempt to justify the consumption of animals, it must be assessed as such. There is no suggestion within the teachings of any of these religions that humans may do as we wish with animals, in fact, there is not a single mainstream religious text which does not devote significant time to discussions of animals and how they should be treated. It is clear that within all mainstream religions animals morally matter, and given that this is the case, it is perfectly reasonable for any person, religious or secular, to conclude that animals matter enough for us to seek to avoid harming or exploiting them wherever possible.