Arguments for vegetarianism can be hard to make in a society where eating bits of animals is so popular, and in an economy where so many people are involved in meat production.

Even if you get over initial objections – What about the loss of jobs? What about the loss of nutrition? – you will encounter more nuanced arguments surrounding the opportunity cost of growing crops.

German philosopher Tatjana Višak, who is speaking at an event in Dublin this week, knows all about such protests. The author of Killing Happy Animals suggests that all living beings have rights and warns against crude utilitarian calculations in moral decision making. This has brought her into conflict with Australian philosopher and fellow vegetarian Peter Singer who has argued that nonhuman animals are "replaceable", meaning it is acceptable to kill them if equally happy animals are created to take their place.

While Singer's position has undergone changes since he published his celebrated book Animal Liberation 40 years ago, his claim that "the premature death of a cow is not a tragedy . . . because whether cows live one year or 10, there is nothing that they hope to achieve" still generates debate.

Višak disagrees with Singer’s logic. Advocating what might seem a radical stance, given our current treatment of nonhuman animals, she argues: “Death is bad in virtue of depriving an individual of future welfare, independently of any specific plans.”

Is the notion of "animal-friendly animal husbandry" a contradiction in terms? "This notion is typically used to refer to husbandry practices in which animals are caused slightly less suffering than in standard practices. For instance, the animals are granted more space. Less suffering is certainly better for these animals than more suffering. But still, they typically suffer a lot.

“Even organic calves, for instance, are usually taken away from their mothers soon after birth. This causes intense suffering for both mother and calf, since their bond is normally tight.

“Stress, boredom and various illnesses due to confinement and handling are frequent among farmed animals. Apart from this, the animals are typically killed at a young age. Is this animal-friendly? I don’t think so.”

If you could ensure that animals produced for meat had a pleasant life before being slaughtered wouldn't it be better for them to have lived than not to have existed at all? "I do not think it can be better for the animals, strictly speaking. Some event benefits me just if due to the event I am better off than I would otherwise have been. That means that, due to the event, my lifetime welfare level were higher than it would otherwise have been.

“Since never existing individuals have no lifetime welfare level, this comparison cannot be made. Therefore existing with a particular welfare level cannot make an individual better or worse off than never existing.

“One might still argue that the amount of welfare in the universe was lower if these well-off animals never existed. That is true. But I do not think that we should care about the quantity of welfare in the universe. Even if having more kids and giving them pleasant lives would maximise the welfare in the universe this gave us no reason, I believe, to have additional kids.

“We cannot harm or benefit the universe as such, we can only harm or benefit sentient individuals. Therefore, our moral duties are restricted to them.”

Peter Singer has argued that self-consciousness makes a difference in this debate, suggesting that beings which lack this capacity are replaceable. What do you think? "Unlike me Peter accepts that, all else [being] equal, we have a reason to bring additional well-off individuals into existence, if only because this maximises the amount of welfare in the universe. Since he is concerned about that quantity of welfare, he accepts that we can painlessly kill some animals and replace them by others, as long as the total amount of welfare in the universe remains unchanged.

“Throughout his career, Peter tried to find reasons for excluding at least self-conscious individuals from this replaceability. Now he accepts it in principle for all individuals, no matter whether or not they are self-conscious.

“Some people argue, as Peter formerly did, that death is a greater harm for individuals that have a conscious desire to go on living and have plans for the future. This requires certain cognitive capacities that some sentient animals assumingly lack. Now Peter thinks, and I agree, that plans for the future do not matter.

“Plans are likely to make a difference if one knows that one is going to die prematurely. But this is irrelevant if we consider an unexpected and painless death. Premature death harms an individual that would otherwise have had a pleasant future, because a longer happy life is better for him or her than a shorter happy life.”

Do nonhuman animals have rights? "Ultimately, I believe, all our normative reasons for action are based on welfare: our own and that of others. Granting animals such as pigs and cows legal rights, including the right to life, may be an efficient way of improving their welfare. We would bring far less of them into existence, but those who existed would have much better lives."

Tatjana Višak will speak at the Vegetarian Society of Ireland's World Vegetarian Day event on Sunday, October 2nd at St Andrew's Resource Centre, 114 Pearse St, Dublin 2. vegetarian.ie

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