“The world of reality has its limits; the world of imagination is boundless.”

Kulturphilosophie (1923), Vol. 2 : Civilization and Ethics
Context: I must interpret the life about me as I interpret the life that is my own. My life is full of meaning to me. The life around me must be full of significance to itself. If I am to expect others to respect my life, then I must respect the other life I see, however strange it may be to mine. And not only other human life, but all kinds of life: life above mine, if there be such life; life below mine, as I know it to exist. Ethics in our Western world has hitherto been largely limited to the relations of man to man. But that is a limited ethics. We need a boundless ethics which will include the animals also.

Source: Rudolf Steiner: The Man and His Vision (1985), p. 161

"Quotes", The Educated Imagination (1963), Talk 1: The Motive For Metaphor http://northropfrye-theeducatedimagination.blogspot.ca/2009/08/1-motive-for-metaphor.html
Context: At the level of ordinary consciousness the individual man is the centre of everything, surrounded on all sides by what he isn't. At the level of practical sense, or civilization, there's a human circumference, a little cultivated world with a human shape, fenced off from the jungle and inside the sea and the sky. But in the imagination anything goes that can be imagined, and the limit of the imagination is a totally human world.

"Quotes", The Educated Imagination (1963), Talk 4: The Keys To Dreamland

Source: Ultramarathon Man: Confessions of an All-Night Runner

Original German:Die Logik erfüllt die Welt; die Grenzen der Welt sind auch ihre Grenzen. Wir können also in der Logik nicht sagen: Das und das gibt es in der Welt, jenes nicht.Das würde nämlich scheinbar voraussetzen, dass wir gewisse Möglichkeiten ausschließen, und dies kann nicht der Fall sein, da sonst die Logik über die Grenzen der Welt hinaus müsste; wenn sie nämlich diese Grenzen auch von der anderen Seite betrachten könnte. Was wir nicht denken können, das können wir nicht denken; wir können also auch nicht sagen, was wir nicht denken können.
1920s, Tractatus Logico-Philosophicus (1922)
Context: Logic pervades the world: the limits of the world are also its limits. So we cannot say in logic, "The world has this in it, and this, but not that." For that would appear to presuppose that we were excluding certain possibilities, and this cannot be the case, since it would require that logic should go beyond the limits of the world; for only in that way could it view those limits from the other side as well. We cannot think what we cannot think; so what we cannot think we cannot say either. (5.61)

"Body Pleasure and the Origins of Violence" (1975)
Context: The world has only a limited time to change its custom of resolving conflicts violently. It is uncertain... how many future generations it will take to transform out psychobiology of violence into one of peace.