 Royce develops an even more systematic argument for an idealism that is both epistemological and ontological in his magnum opus, the two volumes of his 1899–1900 Gifford lectures published as The World and the Individual. As the title suggests, a major theme of this work is explicating in detail the relationship between underlying reality and ordinary individual, conscious human selves. In this book, Royce expounds his idealism as the last of the four possible “conceptions of being”. The first is the “realistic conception of Being”, which is defined by the conception of being as completely independent of thought, so that whatever is true of it is true quite independently of what may be thought about it. The second conception of being is the mystical conception. As the defining notion of the realist conception was independence, the defining notion of mysticism is the opposite, namely immediacy, the idea that thought and its object must be one. The third conception of being, which Royce sometimes calls the theory of “validity”, is that “To be real now means, primarily, to be valid, to be true, to be in essence the standard for ideas” (I:202). This conception of being tries to retain realism’s recognition of independence through the thought that “some of my ideas are already, and apart from my private experience, valid, true, well-grounded” (I:204) and mysticism’s identification of subject and object through the thought that reality is itself possible experience, but adds structure to the now unified realms of thought and being instead of eliminating structure.