We’ve had the pleasure of interviewing some of the world’s leading philosophers, and there has been a subsequent plethora of book recommendations. But recently, we have been pondering what are the absolute most important philosophy books ever written? Which books have shaped how we view philosophy today? Let’s discover, the most important philosophy books ever written.

Let’s now discover the most important Philosophy books ever written…

Julian Baggini:

Aristotle was there at the dawn of Western Philosophy, along with Plato, and the two figures really carved out two different trends in philosophy, which would dominate the rest up until now. Plato was very aspiring to the universal, absolute, unchanging truth – which he thought resided in the world of the forms. Aristotle was a more grounded figure who was looking at how to live from the lens of an imperfect and often by necessity, imprecise knowledge of the good and of the human condition. So, Aristotle was really pioneering a way of doing philosophy of which sort to bring as much rigour as possible to the subject, but not more than the subject matter would allow. That kind of balancing between bringing discipline to thought, but not disciplining so much that you actually do violence to it is very important.

The Ethics, in particular, was important, because it created the idea that being good was a matter of cultivating a certain character that wasn’t about following rules and regulations, which are at best are merely general guidelines to help us on our way. It was about becoming good, by habit, and that being a good person required avoiding extremes. So virtues didn’t have vices as opposites, virtues stood between opposite vices. So for example, courage stands between cowardice and rashness. Aristotle gave us a framework for thinking about how to be good, which is extremely enduring.

Massimo Pigliucci:

When it comes to the most important philosophy books, the foundational book for the entire spectrum of moral philosophies known as virtue ethics. Eudaimonia, the life worth living, is the result of the pursuit of excellence in what distinguishes human beings from the rest of creation: the ability to reason and to act morally. Pursue virtue, which means to develop one’s moral character to the highest degree achievable, and you will be happy, in the sense of realising your human potential. This is done by a combination of reflection (to determine what is the right course of action) and thoughtful repetition (in order to ingrain good habits). Think of it as the moral equivalent of going to the gym to develop your (ethical) muscles.

Robert P. George:

In Natural Law and Natural Rights, originally published in 1980, John Finnis did for the tradition of natural law theory what his mentor, the great Oxford philosopher of law H.L.A. Hart, had done just about twenty years earlier for the tradition of legal positivism in his masterwork, The Concept of Law. He revitalised a classic tradition of thought about law, morality, and their relations by recovering and developing its greatest insights, answering its leading critics, and proposing revisions where thinkers in the tradition had failed or gone astray. In the course of his project, Finnis made important contributions to contemporary debates about practical reason, justice and the common good, authority, obligation, rights, and the problem of legal injustice.

Natural Law and Natural Rights stands alongside The Concept of Law as a classic work in the philosophy of law. At every turn, writers in the field find it necessary to grapple with Finnis’s defence of the Aristotelian-Thomistic tradition of natural law theorising and his criticisms of competing doctrines. As the late Neil MacCormick described Finnis’s book, it provides “a thoroughly challenging account of law, fully capable of standing up to the theories which were regarded as having refuted and superseded it, while taking into account and accepting into its own setting some of the main insights and discoveries of these theories.”

David Papineau:

This lays out the basis for Descartes’ scientific and philosophical system. I have chosen it rather than the more familiar Meditations (with which it overlaps significantly in material) because it makes it much clearer how Descartes’ philosophical ideas relate to his scientific vision. Along with Galileo, Descartes’ was the first great modern scientist, the founder of the mechanical philosophy on which all subsequent science rests. It belittles his philosophical ideas to study them in isolation from his scientific work.

Skye Cleary:

Simone de Beauvoir didn’t intend to be a feminist, but she inadvertently inspired activists and sparked a second wave when she wrote The Second Sex – a groundbreaking manifesto that scrutinised women’s oppression. Her most famous idea, “One isn’t born, but rather becomes, woman,” means that while our anatomy and hormones define our situation, they do not define our roles in society. For example, the ability to have a baby does not automatically mean that one must be a mother and housewife. Since we can’t live authentically unless we’re free to pursue self-chosen goals, Beauvoir calls for men to stop oppressing women, and for women to stop accepting it. In 1949, this was a radical call to action. Yet, it remains vitally relevant even today, as women’s roles and rights in society continue to be challenged.

Massimo Pigliucci:

Actually wrote in collaboration with Mill’s wife, Harriet Tylor, is a crucial and still very much relevant discussion of the limits of personal freedom. Mill and Tylor articulate their famous harm principle, according to which the only reasonable constraint to be imposed on the liberty of individuals is to stop them from doing harm to others. The authors, however, had a very restrictive view of what counts as “harm,” for instance not including hurt feelings, being offended, being outraged, or being disgusted at or by someone else’s behaviourwrittenl and Tylor were concerned by the possibility of a tyranny of the majority in our society and put forth that the best way to deal with wrong ideas is to discuss them in the open, letting truth win out by argument, not by force.

Adrian Moore:

Plato pretty much invented what we now call ‘philosophy’. Whitehead was famously prompted to quip, ‘The safest general characterization of the European philosophical tradition is that it consists of footnotes to Plato.’ Whitehead’s quip may be hyperbolic, but that’s all it is: it is not absurd. One of Plato’s many great dialogues had to feature in my list of the three most important philosophical works. I have chosen his Republic because that is the work in which we see the greatest range, the most representative sample of his views, and the most compelling illustration of his approach to the subject.

Julian Baggini:

I see David Hume, very much as a kind of successor to Aristotle. He too believed in the power of reason, but also deeply appreciated it’s limitations. Hume rejected the Cartesian rationalism which believed that by pure reason alone we could achieve knowledge of what matters in life. He believed the way that we reason is a far more imperfect and almost impossible to justify from a purely logical point of view. It’s a method of generalising from experience for making inferences on the basis of the way things seem to the way we think they are. From a purely logical point of view, this is absolutely outrageous, but we depend upon it.

The idea of cause and effect for example; we can’t conclude by pure reason that there is a thing called ’cause and effect’, nor by observation can we conclude that, because all we actually see is one thing after another. Nonetheless, we must assume there is such a thing as cause and effect in the world in order to make sense of it. There are many other riches to Hume’s thought, but I think what he does like Aristotle, is he get us to use our reason as vigorously as possible, but also pointing out to us what the limits of reason are. He takes us to the edge of reason, and because of that – he is very important.

David Papineau:

Hume was the first western philosopher to work within a non-theological framework. His Treatise (published when he was 28) showed how to understand the nature of humans as natural beings within a natural world. Hume saw clearly how much of previous thinking had to be abandoned, and how much could be preserved. I’m not sure anybody has done a much better job of working out the details of a naturalistic world view in the three centuries since.

Skye Cleary:

Taking to his cherished second-hand desk with a hatchet because a drawer won’t open, Victor Eremita, Kierkegaard’s pseudonymous editor of Either/Or, finds a stash of papers hidden in a secret compartment. One set of letters describes the ecstasy and agony of living a sensual, aesthetic life. The other essays advocate for a more stable and serene ethical lifestyle. Either/Or is like a labyrinth, and there is no clear-cut path or conclusion to which lifestyle readers ought to choose or reach.

Although he drops a few hints, Kierkegaard wanted to provoke readers to think for themselves about what makes for a meaningful life. It was this, as well as his exploration of the personal passionate subjective human experience that retrospectively earned him the reputation of being the first existential philosopher, and his radically different approach to philosophising was why Jean-Paul Sartre called him an anti-philosopher. (I think he meant it as a compliment.)

Adrian Moore:

Although I keep changing my mind about how to rank the most important philosophy books, I have never changed my mind about whether Kant’s Critique of Pure Reason is the greatest. In its depth, breadth, fertility, and endless capacity to stimulate and to fascinate, it stands as an unrivalled monument to philosophical excellence. True, it is sometimes extraordinarily difficult—more difficult, no doubt, than it needs to be. And true, many of its main ideas can no longer be taken seriously. But in the effort to overcome the difficulties of the text, and in the effort to determine why those ideas can no longer be taken seriously, boy does one learn a lot!

Julian Baggini:

If we are talking about the most important philosophy books ever written, then it is impossible not to mention this book, as it is the one which sets the framework for the thinking of a quarter of the world’s population. Confucianism is inseparable from the culture of China. There are other influences there, in particular, Buddhism and Daoism. But, in Confucius, we see the ideals of virtue and the good person, which are actually remarkably similar to Aristotle. But, we also see the high emphasis placed on the value of harmony; in particular social harmony. Social harmony, people living well together is the highest good, and it’s very important to understand that.

One of the most important ideas in Confucian thought is that harmony isn’t about everyone being the same, it’s actually about there being a difference. Just as you need more than one instrument and more than one note to have harmony in music – you need a variety of people and viewpoints to have harmony in society. But that greatest challenge in Confucian thought is to create that harmony from difference. If we could do that, then we can achieve the best world we can ever have. The other striking thing about Confucian philosophy is very much concerned with this world, it’s not really concerned with any higher matters – making it even somewhat agnostic on matters of metaphysics. What really matters is creating the harmonious society in the here and now.

Massimo Pigliucci:

Based on one of Epictetus’ students’ (Arrian of Nicomedia) notes taken while attending the Master’s lectures, it is a very practical introduction to the philosophy of Stoicism, and more broadly a series of discussions on how to live a life worth living. According to Epictetus, the most fundamental thing is to internalise the dichotomy between things that are in our power and things that aren’t, and then focus our energy and resources on the former while facing the latter with equanimity. “Up to us,” as he says, are our judgments, our values, and our actions. The outcomes of those actions, as well as what other people think and do, is not up to us. Many elements of Stoicism were later absorbed by Christianity, and similar ideas are found in Buddhism and Taoism, a remarkable cross-cultural convergence of religious and philosophical traditions.

Robert P. George:

Modern analytical jurisprudence was launched by Herbert Hart in 1960 when Oxford University Press published his book The Concept of Law. While hanging on to legal positivism’s commitment to the idea that there is a “strict conceptual separation between law and morality,” Hart faulted his positivist predecessors, such as Jeremy Bentham and John Austin, for producing “theories that failed to fit the facts” about how law is recognized and functions in actual societies—at least in societies that have moved from a pre-legal order to a regime of law, that is, a social order marked not only by “primary” rules imposing duties, but “secondary” rules of change, adjudication, and recognition.

Hart insisted that laws and legal systems must be understood from the “internal point of view” of officials and others for whom laws function not as “causes” or predictors of what they will do, but as particular sorts of reasons for action—what he later described as “content independent peremptory reasons.” Thus, Hart overturned the so-called “command theory” of law, which proposed to understand laws on the model of “orders backed by threats” and replaced it with a far more sophisticated and refined account of law—one which recognizes not only “duty-imposing” rules, but also “power-conferring” rules that people use to guide their actions and accomplish their goals (such as, entering into a binding contract, establishing a trust, making a will).

David Papineau:

I’m not sure that this will have the same lasting significance as my first two choices, but it has certainly changed the way philosophy has been done in my lifetime. It contains two ideas—externalism about representation, and the difference between necessity and a priority—that just weren’t there when I started doing philosophy. Kripke persuaded us of both of these ideas pretty much single-handed, and they now inform all serious philosophical writing.

Skye Cleary:

Few people make it through Jean-Paul Sartre’s most famous work Being and Nothingness from cover to cover because it’s dreadfully heavy and convoluted in places. Nausea, on the other hand, shows Sartre’s writing at its best. It beautifully illustrates the intense phenomenon of being, the conundrum of coming face-to-face with the absurdity and contingency of existence, and the urgency to create meaning for ourselves. It deals with themes such as freedom, anxiety, and authenticity, that Sartre explored more systematically in Being and Nothingness. Nausea was brilliant enough to be awarded a Nobel Prize for literature in 1964, which Sartre declined. I wouldn’t call it a cheerful novel, but Sartre’s description of existentialism – that it is sternly optimistic – applies to Nausea too.

Adrian Moore:

I struggled for a long time about what to include as the third item on my list. It was very difficult not to include something by Aristotle. But one of the most remarkable features of Aristotle’s corpus is its range, and no single work by him can really testify to this. I eventually settled on Spinoza’s Ethics. This can seem an alien and forbidding work at first, and it is probably best approached in conjunction with a good secondary text that helps the reader to get past these obstacles and to see what Spinoza is up to. (I especially recommend Deleuze’s Expressionism in Philosophy.) The result is a remarkably powerful ethical system, almost all of whose main ideas—in contrast to what I said about Kant’s Critique of Pure Reason—can still be taken seriously.

Vote on the most important Philosophy book…

Meet our Expert Panel

To compile a list of the most important philosophy books ever written, we needed to assemble a panel of incredible minds who span the subject of philosophy from a multitude of angles. So, we reached out to some of our most renowned philosophy guests and enquired as to whether they’d be happy to provide us with their personal votes. We asked each expert to select a few books they felt were the most important philosophy books, and to provide their reasoning. As a result, we have a wonderful list of books that I feel you will thoroughly enjoy.

Julian Baggini is one of the UK’s leading philosophers, having authored several books, including Welcome to Everytown: A Journey into the English Mind, The Philosopher’s Toolkit and more recently Freedom Regained: The Possibility of Freewill. On top of this, Julian is also a regular contributor to a selection of newspapers and magazines, including the Guardian, Prospect and the Financial Times.

Skye Cleary is a philosopher and author who also teaches at Columbia University, Barnard College and the City College of New York. She published her book, Existentialism and Romantic Love in 2015, and is also the Managing Editor of the American Philosophical Association’s blog, an advisory board member of Strategy of Mind, and a certified fellow with the American Philosophical Practioners Association.

Massimo Pigliucci earned a doctorate in genetics from the University of Ferrara, Italy, and then a PhD in biology from the University of Connecticut, and finally a PhD in philosophy of science from the University of Tennessee. He was formerly a professor of ecology and evolution at Stony Brook University. In 1997, he received the Theodosius Dobzhansky Prize and is also a regular contributor to Skeptical Inquirer.

Robert P. George holds Princeton’s celebrated McCormick Chair in Jurisprudence. Previously, Robert P. George served as chairman of the United States Commission on International Religious Freedom (USCIRF), and before that on the President’s Council on Bioethics and as a presidential appointee to the United States Commission on Civil Rights. He has written many books, and his most recent book is Conscience and Its Enemies.

Adrian Moore is a Professor of Philosophy at the University of Oxford, whose main philosophical areas of focus include Kant, Wittgenstein, history of philosophy, metaphysics, philosophy of mathematics and philosophy of logic. He is also a prolific writer. His first book, The Infinite, was considered an ‘authoritative overview of a topic of considerable philosophical importance’.

At the University of Natal, David Papineau studied mathematics and statistics for four years. In 1968, David returned to England to study philosophy at Cambridge and then completing a PhD on conceptual change and scientific rationality. David Papineau was the President of the British Society for Philosophy of Science for 1993-5, President of the Mind Association for 2009-10, and President of the Aristotelian Society for 2013-14.

I hope you have enjoyed discovered what the panel believes to be the most important philosophy books; if you have, you may also enjoy the best philosophy books for beginners. If you think our panel have missed one of the most important philosophy books, comment below with which books would get your vote!