Søren Kierkegaard has long been considered the father of the philosophical movement known as Christian existentialism, which focuses on the living human being. In his major 1849 work, The Sickness unto Death, he takes listeners on a journey from the human self, its spirit, despair and sin, through to faith.

This first new translation of Kierkegaard's masterwork in a generation brings an essential work of modern philosophy to vivid life. While the majority of Kierkegaard's work leading up to The Concept of Anxiety dealt with the intersection of faith and knowledge, here the renowned Danish philosopher turns to the perennial question of sin and guilt. First published in 1844, this concise treatise identified - long before Freud - anxiety as a deep-seated human state, one that embodies the endless struggle with our own spiritual identities.

On the Genealogy of Morality was written in 1887 when Friedrich Nietzsche was at the height of his powers as a philosopher and master of German prose writing. Here, he criticizes the idea that there is just one conception of moral goodness, dissecting the contemporary practice of morality and looking at it from a historical viewpoint. Rather than following a metaphysical or religious approach, Nietzsche adopts a naturalistic framework, which is grounded in history and natural science, to understand our concepts of good and evil in the Christianized Western world.

From the perspective of an unbeliever, Fear and Trembling explores the paradox of faith, the nature of Christianity, and the complexity of human emotion. Kierkegaard examines the biblical story of Abraham, who was instructed to sacrifice his son Isaac, and forces us to consider Abraham's state of mind. What drove Abraham, and what made him carry out such an absurd and extreme request from God? Kierkegaard argues that Abraham's agreement to sacrifice Isaac, and his suspension of reason, elevated him to the highest level of faith.

A work that had a huge influence on great thinkers including celebrated German philosopher Immanuel Kant, An Enquiry is Hume's examination of how we obtain information and form beliefs. He argues that we mainly gain knowledge through our senses, a theory known as empiricism. But while the impressions from our senses are key to our beliefs about the world, Hume argues that reason and facts play only a limited part.