For centuries philosophers have attached much importance to a priori knowledge, but recent work in epistemology and experimental philosophy has questioned this. Leading philosophers discuss explanations of the a priori, challenges to its existence, the status of intuition, and the justification of belief—topics at the centre of current debate.

Widely praised as a founder of modern semiotics and of the pragmatist tradition in philosophy, Charles S. Peirce (1839-1914) spent over forty years developing a philosophical system that addresses the fundamental problems of Western metaphysics, epistemology, and value theory. Although never formally completed, what emerges from Peirce’s writings is a distinctive system, through an innovative semiotic or theory of signs and cognition, that combines with a robustly realist metaphysics that emphasizes the mind-independence of laws and other universals. Peirce’s Empiricism: Its Roots and Its Originality explains this marriage of empiricism with realism by tracing the roots of Peirce’s thought in the history of Western philosophy, with particular attention paid to his predecessors in the empiricist and the common sense traditions. By purging modern empiricism of its nominalistic metaphysics and its Cartesian assumptions about mind and knowledge, and by combining it with insights from sources as diverse as Duns Scotus and Charles Darwin, Peirce reinvents the idea that all our knowledge depends on sense perception while reaffirming the place of philosophy as a foundational field of inquiry. In Peirce’s Empiricism, Aaron Bruce Wilson defends an interpretation of Peirce’s philosophical work as forming a systematic whole, and develops the connections between Peirce, Reid, and the British empiricists. Wilson provides focused analyses of Peirce’s accounts of experience, habit, perception, semeiosis, truth, and ultimate ends. This book will be of great value to students and scholars with interests in Peirce, American philosophy more broadly, modern philosophy, and semiotics.

The ontological argument for the existence of God has been a constant in the philosophy of religion since its first formulation by Anselm of Canterbury in the 11th century. In the 17th century, it was revived by Ren Descartes, and ever since has been a subject of dispute and much debate among philosophers. Descartes formulated it as follows: "Premise 1: That which we clearly understand to belong to the true and immutable nature, or essence, or form of something, can be truly asserted of that thing. "Premise 2: But once we have made a sufficiently careful investigation into what God is, we clearly and distinctly understand that existence belongs to his true and immutable nature. Conclusion: Hence we can now truly assert of God that he does exits" In this interesting history of the argument, philosopher Kevin J. Harrelson shows that the defense of the ontological argument is more consistent and persuasive than has frequently been supposed. In addition to correcting many common misunderstandings about the argument, the author highlights what appears to be an irremovable tension between the conclusion and the explanation of the proof. Both the common objections to the argument and its historical development in early modern philosophy are explained in light of this tension.

Rational Intuition explores the concept of intuition as it relates to rationality through mediums of history, philosophy, cognitive science, and psychology.

A comprehensive defence of the rationalist view that insight independent of experience is a genuine basis for knowledge.

Perhaps the most famous proposition in the history of philosophy is Descartes' cogito 'I think, therefore I am'. Husain Sarkar claims in this provocative interpretation of Descartes that the ancient tradition of reading the cogito as an argument is mistaken. It should, he says, be read as an intuition. Through this interpretative lens, the author reconsiders key Cartesian topics: the ideal inquirer, the role of clear and distinct ideas, the relation of these to the will, memory, the nature of intuition and deduction, the nature, content and elusiveness of 'I', and the tenability of the doctrine of the creation of eternal truths. Finally, the book demonstrates how Descartes' attempt to prove the existence of God is foiled by a new Cartesian Circle.