That there is a casual relationship between the cruelty, torture, and death of human beings and the ongoing slaughter of millions of pigs, cows, fowl, and sheep, not to mention whales, dolphins, and seals, must be obvious to anyone aware of the interrelation of all forms of existence and of the karmic repercussions of our actions. By our consumption of meat we allow this carnage to continue and are part perpetrators. And because of the cause-effect relationship, we are also part victims.
How is it possible to swallow the carcasses of these slain creatures, permeated as they are with the violent energy of the pain and terror experienced by them at the time of their slaughter, and not have hatred, aggression, and violence stimulated in oneself and others? “While we ourselves are the living graves of murdered beasts,” asks George Bernard Shaw, “how can we expect any ideal conditions on the earth?” This sentiment is echoed in an ancient Chinese verse [as above] that vividly describes the evil karma generated by the killing of animals:
For hundreds of thousands of years the stew in the pot
has brewed hatred and resentment that is difficult to stop.
If you wish to know why there are disasters of armies and weapon in the world,
listen to the piteous cries from the slaughterhouse at midnight.
To Cherish All Life: A Buddhist Case For Becoming Vegetarian
Roshi Philip Kapleau