Ethics in the Real World: 82 Brief Essays on Things That Matter. By Peter Singer. Princeton University Press; 355 pages; $27.95 and £19.95.

SEARCH on Google, buy products on Amazon or share a friend’s post on Facebook and, after a while, the invisible algorithms that underpin these websites will start subtly changing their offerings in an effort to please. As algorithms like these improve the way they serve up content that people like, they may create for their users a false, virtual world where their values go unchallenged.

Those wishing to escape this cosy cocoon should welcome a robust test of the ethical assumptions by which they live. There are few people better qualified to provide this challenge than Peter Singer, a moral philosopher and professor of bioethics at Princeton University. “Animal Liberation”, an earlier book by Mr Singer, is credited with giving the animal-rights movement intellectual heft. “The Life You Can Save”, which proposes minimum ethical standards for charitable donations, was cited by Melinda Gates in an interview about “The Giving Pledge”, a campaign to encourage billionaires to give the majority of their fortunes to good causes (over 150 have signed so far).

Mr Singer’s latest book, “Ethics in the Real World”, is a collection of 82 essays, each rarely more than three or four pages long. As such, it is an accessible introduction to the work of a philosopher who would not regard being described as “accessible” as an insult. As Mr Singer notes drily in the introduction, “I suspect that whatever cannot be said clearly is probably not being thought clearly either.”

Despite their brevity, the essays do not shirk the big moral questions including perhaps the biggest of all: can there be objectively true answers to the question of how one ought to act? In a piece about “On What Matters” by Derek Parfit, a philosopher, Mr Singer distils more than 1,400 pages of argument down to a scant three and concurs with him that moral judgments can, indeed, be true or false.

Most of Mr Singer’s book, though, deals with pressing contemporary moral issues including abortion (he argues that the interests of a conscious, rational being trump those of the fetus, which only has the potential to become self-aware in the future), voluntary euthanasia (he is in favour) and the importance of acting to prevent catastrophic climate change.

Perhaps the most arresting essay is a previously unpublished piece in which Mr Singer urges readers to spare a thought for the poor, benighted turkey during Thanksgiving. The breast of the standard American turkey has become so enlarged by selective breeding that it can no longer mate because the male’s breast gets in the way. Mr Singer describes how thousands of such sexually disabled male turkeys are masturbated by workers and the females artificially inseminated using the tube of an air compressor (at the rate of one every 12 seconds at one turkey farm). Mr Singer advises serving a vegetarian Thanksgiving meal or, at the very least, forking out for a more expensive heritage breed that has been raised humanely.

Agree with him or not, Mr Singer practises what he preaches. He has not eaten meat for more than 40 years, and in 1996 he stood (unsuccessfully) as a Senate candidate for the Australian Greens. One essay from 2012 celebrates the European Union’s ban on the use of battery cages for hens, a ban he and others helped to bring about through protests beginning in the 1970s.

However, agreeing with Mr Singer that objective ethical truths exist and imagining anyone, even a moral philosopher, has a monopoly on divining what these might be are not the same. Among the best essays in this collection are those that demonstrate that Mr Singer is alive to the possibility of being wrong. In “A Clear Case for Golden Rice” he admits that “none of the disastrous consequences” that Greens feared would result from planting genetically modified (GM) crops have come to pass and some GM crops may have a role to play in public health or in feeding the planet in an era of climate change. A welcome admission that even a much-feted moral philosopher may sometimes err.