What is Carnism?

Taken directly from the Carnism website www.carnism.com, this is the definition of Carnism.  This website is extremely interesting and might add a whole new dimension to the question, "Why do we eat meat?"

Carnism is the invisible belief system, or ideology, that conditions people to eat certain animals. Carnism is essentially the opposite of vegetarianism or veganism; “carn” means “flesh” or “of the flesh” and “ism” denotes a belief system. Most people view eating animals as a given, rather than a choice; in meat-eating cultures around the world people typically don’t think about why they find the meat of some animals disgusting and the meat of other animals appetizing, or why they eat any animals at all. But when eating animals isn’t a necessity for survival, as is the case in the majority of the world today, it is a choice - and choices always stem from beliefs.

We recognize that not eating animals stems from a belief system; vegetarianism was named centuries ago. Accordingly, we don't refer to vegetarians as "plant eaters," as we understand that eating plants reflects an underlying ideology in which consuming animals is considered unethical and inappropriate. Yet, we still refer to "non-vegetarians" as "meat eaters," as though the act of eating meat were divorced from a belief system, as though vegetarians were the only ones who bring their beliefs to the dinner table. However, the reason that many people eat pigs but not dogs, for example, is because they do have a belief system when it comes to eating animals.
Why, then, has carnism not been named until now? One reason is because it's simply easier to recognize those ideologies that fall outside the mainstream. A much more important reason, though, is because carnism is a dominant ideology - an ideology so widespread and entrenched that its tenets are considered common sense, "the way things are," rather than a set of widely held opinions. And carnism is also a violent, exploitative ideology; it is organized around intensive, extensive, and unnecessary violence toward, and exploitation of, animals. Even the production of so-called humane meat (and other animal products), a miniscule percentage of the meat produced in the world today, exploits animals and often involves brutality. The tenets of carnism run counter to the core values of most people who would not willingly support the exploitation of others or condone such violence toward other sentient beings. So carnism, like other violent, exploitative ideologies, must hide itself to ensure the participation of the populace; without popular support, the system would collapse.

Omnivore and Carnivore: Inaccurate Terms

Just as "meat eater" is an inaccurate and misleading phrase to describe those who are not vegetarian, so, too, are the other commonly used terms, "omnivore" and "carnivore." These terms reinforce the assumption that eating animals is natural, one of the most entrenched and compelling myths used to justify carnism. "Omnivore" and "carnivore" describe one's physiological disposition, rather than one's ideological choice: an omnivore is an animal, human or nonhuman, that can ingest both plant and animal matter, and a carnivore is an animal that needs to ingest flesh in order to survive.

Carnistic Defenses

Ideologies such as carnism keep themselves alive by teaching us not to think or feel when we follow their dictates, and one of the primary ways they do this is by using a set of defense mechanisms which operate on both the social and psychological levels. "Carnistic defenses" hide the contradictions between our values and behaviors, allowing us to make exceptions to what we would normally consider ethical.
The primary defense of the system is invisibility and the primary way the ideology stays invisible is by remaining unnamed: if we don't name it, we won't see it, and if we don't see it, we can't talk about it or question it. But not only is the ideology itself invisible, so, too, are the victims of the system: the trillions of farmed animals who remain out of sight and therefore conveniently out of public consciousness; the increasingly degraded environment; the exploited and often brutalized meat packers and slaughterhouse workers; and the human meat consumers who are at increased risk for some of the most serious diseases of the industrialized world and who have been conditioned to disconnect, psychologically and emotionally, from the truth of their experience when it comes to eating animals.
But invisibility is only the first line of defense in the fortress of carnism; the truth is impossible to completely obscure. So when invisibility inevitably falters, the system needs a backup. Hence, carnism teaches us to justify eating animals, and it does this by presenting the myths of meat (and other animal products) as though they were the facts of meat, by promoting the Three Ns of Justification: eating animals is normal, natural, and necessary. The Three Ns are institutionalized - they are embraced and maintained by all major social institutions, from the family to the state - and, perhaps not surprisingly, they have been invoked throughout history to justify other violent, exploitative ideologies (e.g., slavery, male dominance, etc.).
Carnism also defends itself by distorting our perceptions of meat and the animals we eat so that we can feel comfortable enough to consume them. We learn, for instance, to view farmed animals as objects (e.g., we refer to a chicken as something, rather than someone) and as abstractions, lacking in any individuality or personality (e.g., a pig is a pig and all pigs are the same), and to create rigid categories in our minds so that we can harbor very different feelings and behaviors toward different species (e.g., beef is delicious and dog meat is disgusting; cows are for eating and dogs are our friends).
There are a number of other defenses that overlap with and support those mentioned here, but all defenses serve a single purpose: to block our awareness and empathy when it comes to farmed animals and the products procured by their bodies. With awareness of carnistic defenses, though, we are less vulnerable to their influence; we are able to step outside the system and look at the issue of eating animals through our own eyes, rather than through the lens of carnism.