The following dialogue contains nine arguments. Translate each into symbolic form and then use the eighteen rules of inference to derive the conclusion of each. Some of them are quite challenging.

Where’s the Beef?

“Have you decided what to order?” Paul says to Mindy, as he folds his menu and puts it on the table.
“I think I’ll have the tofu stir-fry,” she replies. “And you?”
“I’ll have the rib steak,” Paul says. “You know the rib steak is really good here, and so is the pork tenderloin.”
“I’m a vegetarian,” she says.
“Oh,” Paul says. He smiles sheepishly.
Mindy smiles too. “First date,” she says.
“Yeah,” says Paul. “What made you decide to become a vegetarian?”
“For one thing,” Mindy says, “I think a vegetarian diet is healthier. People who eat meat increase their intake of cholesterol and carcinogens. Those who increase their intake of cholesterol run a higher risk of heart attack, and those who increase their intake of carcinogens run a higher risk of cancer. Anyone who runs a higher risk of heart attack and cancer is less healthy. Thus, people who eat meat are less healthy.

“I might add that if people who eat meat are less healthy, then if parents are responsible, then they will refrain from feeding meat to children. All parents love their children, and if they do, then they are responsible. But if parents refrain from feeding meat to children, then children will grow up to be vegetarians. And if that happens, then nobody will eat meat in the future. Thus, we can look forward to a future where everyone is a vegetarian.”

“Well, I won’t hold my breath on that,” Paul says, as he offers Mindy a slice of bread from the basket on the table. “If children and teenagers fail to eat meat, then they become deficient in zinc. And if children become deficient in zinc, then they risk a weakened immune system. And if that happens, then they are less healthy. Also, if elderly people fail to eat meat, then they become deficient in iron. And if elderly people become deficient in iron, then they risk becoming anemic, and if that happens, they are less healthy. Therefore, if children and elderly people fail to eat meat, then they are less healthy.”

Mindy smiles. “That’s what zinc tablets and iron supplements are for,” she says. Anyway, there are also moral reasons for being a vegetarian. Consider this. Animals are sentient beings—they feel pain, fear, and joy—and they have an interest in preserving their lives. If animals are sentient, then if humans cause animals to suffer, then they act immorally. And if animals have an interest in preserving their lives, then if humans exploit animals, then they act immorally. But if humans kill animals for food, then they cause animals to suffer or they exploit them. Therefore, if humans kill animals for food, then they act immorally.”

“I agree with you that animals should not be made to suffer,” Paul responds. “But if animals are raised under humane conditions, and some of them are, then they will not be caused to feel pain or distress. And if animals are not caused to feel pain, then we are morally justified in eating them. Thus, we are morally justified in eating some animals.”

“I disagree,” says Mindy.
“That’s because you think that animals have rights,” Paul says. “If animals have rights, then they have moral judgment. And if animals have moral judgment, then they respect the rights of other animals. But every animal pursues its own self-interest to the exclusion of other animals, and if that’s so, then it does not respect the rights of other animals. Therefore, animals have no moral judgment and they also have no rights.”

“Well,” Mindy replies, “by that line of reasoning infants and mentally challenged adults have no rights. But everyone recognizes that they do have rights. And if infants have rights, then some people who lack the capacity for moral judgment have rights. But if this is true, then animals have rights, and if they do, then surely they have the right to life. But if animals have the right to life, then if humans are moral, then they must respect that right and they cannot kill animals for food. Thus, if humans are moral, they cannot kill animals for food.”

“The question of infants and mentally challenged adults raises an interesting point,” Paul says. “I think what it comes down to is this: Something is considered to have rights if and only if it looks human. Infants and mentally challenged adults look human, so they are considered to have rights. But animals do not look human, so they are not considered to have rights.”
“That sounds awfully arbitrary,” says Mindy. “But I think what it really comes down to is power. Something is considered to have rights if and only if it has as much power as humans. Animals do not have as much power as humans, so animals are not considered to have rights. But that seems terribly wrong to me. It shouldn’t be a question of power. Anyway, now that our food has arrived, how’s your steak?”

Paul takes a bite. “It’s great,” he says. “And how’s your stir-fry?”
“Great,” Mindy says. She laughs. “And so is my conscience.”