Throughout history philosophers have sought to define, understand, and delineate concepts important to human well-being. One such concept is "knowledge." Many philosophers believed that absolute, certain knowledge, is possible—that the physical world and ideas formulated about it could be given solid foundation unaffected by the varieties of mere opinion.

Immanuel Kant’s Critique of Pure Reason can lay claim to being the most important single work of modern philosophy, a work whose methodology, if not necessarily always its conclusions, has had a profound influence on almost all subsequent philosophical discourse. In this work Kant addresses, in a groundbreaking elucidation of the nature of reason, the age-old question of philosophy: “How do we know what we know?” and the limits of what it is that we can know with certainty.

A Treatise of Human Nature is the first work ever published by David Hume, a man who revolutionized our understanding of philosophy. Hume was an advocate of the skeptical school of philosophy and a key figure in the Scottish Enlightenment. He looks at the nature of human experience and cognition, showing that philosophy and reason can only be reflections of our nature.

On Liberty is a book by John Stuart Mill, one of the most celebrated philosophers on the subject of leadership and governing ideals. The book focuses on Mill's philosophy on utilitarianism which is one of his defining principles. The principles of the book are focused on developing a relationship between the ruling authority and liberty.

The Republic poses questions that endure: What is justice? What form of community fosters the best possible life for human beings? What is the nature and destiny of the soul? What form of education provides the best leaders for a good republic? What are the various forms of poetry and the other arts, and which ones should be fostered and which ones should be discouraged? How does knowing differ from believing?

Both astonishing and prophetic, The Abolition of Man remains one of C. S. Lewis's most controversial works. Lewis sets out to persuade his audience of the ongoing importance and relevance of universal objective values, such as courage and honor, and the foundational necessity of natural law. He also makes a cogent case that a retreat from these pillars of our educational system, even if in the name of "scientism", would be catastrophic. National Review lists it as number seven on their "100 Best Nonfiction Books of the 20th Century".

"The central miracle asserted by Christians is the Incarnation. They say that God became Man. Every other miracle prepares the way for this, or results from this." This is the key statement of Miracles, in which C. S. Lewis shows that a Christian must not only accept but rejoice in miracles as a testimony of the unique personal involvement of God in his creation.

Considered to be one of the most important philosophical works of all time, the History of Western Philosophy is a dazzlingly unique exploration of the ideologies of significant philosophers throughout the ages - from Plato and Aristotle through to Spinoza, Kant and the 20th century. Written by a man who changed the history of philosophy himself, this is an account that has never been rivaled since its first publication over 60 years ago.

Schopenhauer was just 30 when his magnum opus, Die Welt als Wille und Vorstellung, a work of considerable learning and innovation of thought, first appeared in 1818.

Much to his chagrin and puzzlement (so convinced was he of its merits), it didn't have an immediate effect on European philosophy, views and culture. It was only decades later that it was recognised as one of the major intellectual landmarks of the 19th century.

Critique of Judgement was published in 1790 and is divided into two parts, the Critique of Aesthetic Judgement and the Critique of Teleological Judgement. Our ‘judgements of taste’, as Kant describes our aesthetic judgements, have both a personal and a universal function: personal, because we have a subjective aesthetic response to the ‘agreeable’, the ‘beautiful’, the ‘sublime’ and the ‘good’; but also there is a ‘universal’ aspect because our aesthetic response has a ’disinterested’ element. This brings under Kant’s spotlight, for example, the concept of beauty and the perception of beauty.

Immanuel Kant's Fundamental Principles of the Metaphysics of Morals, first published in 1785, lays out Kant's essential philosophy and defines the concepts and arguments that would shape his later work. Central to Kant's doctrine is the categorical imperative, which he defines as a mandate that human actions should always conform to a universal, unchanging standard of rational morality.

John Locke and his works - particularly An Essay Concerning Human Understanding - are regularly and rightly presented as foundations for the Age of Enlightenment. His primary epistemological message - that the mind at birth is a blank sheet waiting to be filled by the experiences of the senses - complemented his primary political message: that human beings are free and equal and have the right to envision, create and direct the governments that rule them and the societies within which they live.

The Problems of Philosophy discusses Bertrand Russell's views on philosophy and the problems that arise in the field. Russell's views focus on knowledge rather than the metaphysical realm of philosophy. The Problems with Philosophy revolves around the central question that Russell asks in his opening line of Chapter 1 - Is there any knowledge in the world which is so certain that no reasonable man could doubt it?

Philosophy of Mind is the third and final part of the Encyclopaedia of the Philosophical Sciences, the collection in which Hegel (1730-1831) offered an overview of his life’s work. Though originally written in 1817, he revised it in 1830, thus providing a finished form the year before his death. Hegel used the three parts of the Encyclopaedia - Science of Logic, Philosophy of Nature and Philosophy of Mind - as a basis for lectures at the Universities of Heidelberg which he joined in 1816, and in Berlin in 1820.

There is a cause, or a reason, behind everything that happens. This is the fundamental view behind the classical proposition the Principle of Sufficient Reason, which, in 1813, Schopenhauer chose as his subject for further examination in his doctoral dissertation On the Fourfold Root of the Principle of Sufficient Reason....

Immanuel Kant's Fundamental Principles of the Metaphysics of Morals, first published in 1785, lays out Kant's essential philosophy and defines the concepts and arguments that would shape his later work. Central to Kant's doctrine is the categorical imperative, which he defines as a mandate that human actions should always conform to a universal, unchanging standard of rational morality.

John Locke and his works - particularly An Essay Concerning Human Understanding - are regularly and rightly presented as foundations for the Age of Enlightenment. His primary epistemological message - that the mind at birth is a blank sheet waiting to be filled by the experiences of the senses - complemented his primary political message: that human beings are free and equal and have the right to envision, create and direct the governments that rule them and the societies within which they live.

The Problems of Philosophy discusses Bertrand Russell's views on philosophy and the problems that arise in the field. Russell's views focus on knowledge rather than the metaphysical realm of philosophy. The Problems with Philosophy revolves around the central question that Russell asks in his opening line of Chapter 1 - Is there any knowledge in the world which is so certain that no reasonable man could doubt it?

There is a cause, or a reason, behind everything that happens. This is the fundamental view behind the classical proposition the Principle of Sufficient Reason, which, in 1813, Schopenhauer chose as his subject for further examination in his doctoral dissertation On the Fourfold Root of the Principle of Sufficient Reason....

This expanded edition of John Stuart Mill's Utilitarianism includes the text of his 1868 speech to the British House of Commons defending the use of capital punishment in cases of aggravated murder. The speech is significant both because its topic remains timely and because its arguments illustrate the applicability of the principle of utility to questions of large-scale social policy.

Considered by many to be Hannah Arendt's greatest work, published as she neared the end of her life, The Life of the Mind investigates thought itself, as it exists in contemplative life. In a shift from her previous writings, most of which focus on the world outside the mind, this work was planned as three volumes that would explore the activities of the mind considered by Arendt to be fundamental. What emerged is a rich, challenging analysis of human mental activity, considered in terms of thinking, willing, and judging.

Kant published this work in 1795, during the aftermath of the American Revolution and the French Revolution. The high hopes of the European Enlightenment had been dampened by the Reign of Terror in which tens of thousands of people died, and the perpetual cycle of war and temporary armistice seemed to be inescapable. Kant's essay is best known as an early articulation of the idea of a league of nations that could bring an end to all hostilities. Today, the United Nations continues to pursue that dream, but lasting peace still seems to be wishful thinking.

On Liberty is a book by John Stuart Mill, one of the most celebrated philosophers on the subject of leadership and governing ideals. The book focuses on Mill's philosophy on utilitarianism which is one of his defining principles. The principles of the book are focused on developing a relationship between the ruling authority and liberty.

Whitehead presented these three lectures at Princeton University in 1929. Although 85 years have passed, his central thesis and his analysis remain remarkably current. The scientific materialism that Whitehead opposed with such vigor continues to dominate in academic circles, and even now those who question that worldview are often accused of being antiscientific. This is especially true in discussions of the nature of the human mind and its relation to the body (particularly the brain).

In The Dream of Enlightenment, Anthony Gottlieb expertly navigates a second great explosion of thought, taking us to northern Europe in the wake of its wars of religion and the rise of Galilean science. In a relatively short period - from the early 1640s to the eve of the French Revolution - Descartes, Hobbes, Spinoza, Locke, Leibniz, and Hume all made their mark. The Dream of Enlightenment tells their story and that of the birth of modern philosophy.

Hannah Arendt's insightful observations of the modern world, based on a profound knowledge of the past, constitute an impassioned contribution to political philosophy. In Between Past and Future, Arendt describes the perplexing crises modern society faces as a result of the loss of meaning of the traditional key words of politics: justice, reason, responsibility, virtue, and glory. Through a series of eight exercises, she shows how we can redistill the vital essence of these concepts and use them to regain a frame of reference for the future.

The Crowd: A Study of the Popular Mind is a seminal work on crowd psychology by Gustave Le Bon (1841-1931), a French social psychologist. He observes that a crowd forms when an influential idea unites a number of individuals and prompts them to act towards a common goal. In a crowd, the conscious personality of the individual is submerged and dominated by the collective mind. Furthermore, every sentiment becomes contagious to a degree that individuals readily sacrifice their personal interest to the collective.

A dialogue between Socrates and Meno probes the subject of ethics. Can goodness be taught? If it can, then we should be able to find teachers capable of instructing others about what is good and bad, right and wrong, or just and unjust.

Where did the ideas come from that became the cornerstone of American democracy? Not only the erudite Thomas Jefferson, the wily and elusive Ben Franklin, and the underappreciated Thomas Paine, but also Ethan Allen, the hero of the Green Mountain Boys, and Thomas Young, the forgotten Founder who kicked off the Boston Tea Party. These radicals who founded America set their sights on a revolution of the mind. Derided as "infidels" and "atheists" in their own time, they wanted to liberate us not just from one king but from the tyranny of supernatural religion.

Despite the recent ferocious public debate about belief, the concept most central to the discussion "God" frequently remains vaguely and obscurely described. Are those engaged in these arguments even talking about the same thing? In a wide-ranging response to this confusion, esteemed scholar David Bentley Hart pursues a clarification of how the word "God” functions in the world’s great theistic faiths.