"The World as Will and Idea" is the central work of the German philosopher Arthur Schopenhauer. Taking the transcendental idealism of Immanuel Kant as his starting point, Schopenhauer argues that the world we experience around us – the world of objects in space and time and related in causal ways – exists solely as "representation" dependent on a cognizing subject, not as a world that can be considered to exist in itself. Our knowledge of objects is thus knowledge of mere phenomena rather than things-in-themselves. Schopenhauer identifies the thing-in-itself – the inner essence of everything – as will: a blind, unconscious, aimless striving devoid of knowledge, outside of space and time, and free of all multiplicity. The world as representation is, therefore, the "objectification" of the will. "The World as Will and Idea" marked the pinnacle of Schopenhauer's philosophical thought; he spent the rest of his life refining, clarifying, and deepening the ideas presented in this work without any fundamental changes.