Skepticism refers to the philosophic position holding that the possibility of knowledge is limited either because of the limitations of the mind or because of the inaccessibility of its object. It is more loosely used to denote any questioning attitude. Extreme skepticism holds that no knowledge is possible, but this is logically untenable since the statement contradicts itself. During the Renaissance the influence of ancient skepticism was reflected preeminently in the writings of the 16th-century French philosophical essayist Michel de Montaigne. The greatest exponent of modern skepticism was the 18th-century Scottish empiricist philosopher David Hume. In his Treatise of Human Nature and An Enquiry Concerning Human Understanding , Hume questions the possibility of demonstrating the truth of beliefs about the external world, causal connections, future events, or such metaphysical entities as the soul and God. The 18th-century German philosopher Immanuel Kant, while attempting to overcome Humes skepticism, denied the possibility of knowing things in themselves or of achieving metaphysical knowledge. In the 19th century, the German philosopher Friedrich Nietzsche denied the possibility of complete objectivity, and thus of objective knowledge, in any field. The 20th-century American philosopher George Santayana, claiming to have taken Humes skepticism a step further, maintained, in his work Scepticism and Animal Faith , that belief in the existence of anything, including oneself, rests on a natural, but irrational impulse. Elements of skepticism may be found in other modern schools of philosophy, including pragmatism, analytic and linguistic philosophy, and existentialism.
