“All that is not thought is pure nothingness”

Source: Religion and Nothingness (1983), p. 70

Japan, the Beautiful and Myself (1969)
Context: The Zen disciple sits for long hours silent and motionless, with his eyes closed. Presently he enters a state of impassivity, free from all ideas and all thoughts. He departs from the self and enters the realm of nothingness. This is not the nothingness or the emptiness of the West. It is rather the reverse, a universe of the spirit in which everything communicates freely with everything, transcending bounds, limitless. There are of course masters of Zen, and the disciple is brought toward enlightenment by exchanging questions and answers with his master, and he studies the scriptures. The disciple must, however, always be lord of his own thoughts, and must attain enlightenment through his own efforts. And the emphasis is less upon reason and argument than upon intuition, immediate feeling. Enlightenment comes not from teaching but through the eye awakened inwardly. Truth is in "the discarding of words", it lies "outside words". And so we have the extreme of "silence like thunder", in the Vimalakirti Nirdesa Sutra.

Source: The Complex Vision (1920), Chapter I
Context: One of the curious psychological facts, in connection with the various ways in which various minds function, is the fact that when in these days we seek to visualize, in some pictorial manner, our ultimate view of life, the images which are called up are geometrical or chemical rather than anthropomorphic. It is probable that even the most rational and logical among us as soon as he begins to philosophize at all is compelled by the necessity of things to form in the mind some vague pictorial representation answering to his conception of the universe.
Most minds see the universe of their mental conception as something quite different from the actual stellar universe upon which we all gaze. Even the most purely rational minds who find the universe in "pure thought" are driven against their rational will to visualize this "pure thought" and to give it body and form and shape and movement.

Source: Pène du Bois (1897), p. 96.

A ceux qui ont épuisé la politique, il ne reste plus que la pensée pure.
Source: About Catherine de' Medici (1842), Part II: The Ruggieri's Secret, Ch. V: The Alchemists.

“Pure Thought,” p. 90
The Creator (2000), Sequence: “Nostalgic Elements”

from On the Method of Theoretical Physics, p. 183. The Herbert Spencer Lecture, delivered at Oxford (10 June 1933). Quoted in Einstein's Philosophy of Science http://plato.stanford.edu/entries/einstein-philscience/
1930s
Context: Our experience hitherto justifies us in trusting that nature is the realization of the simplest that is mathematically conceivable. I am convinced that purely mathematical construction enables us to find those concepts and those lawlike connections between them that provide the key to the understanding of natural phenomena. Useful mathematical concepts may well be suggested by experience, but in no way can they be derived from it. Experience naturally remains the sole criterion of the usefulness of a mathematical construction for physics. But the actual creative principle lies in mathematics. Thus, in a certain sense, I take it to be true that pure thought can grasp the real, as the ancients had dreamed.

In 'Celebració de la mel', Antoni Tàpies, in La peinture et le vide, Fundació Antoni Tàpies, Barcelona, 1993, p. 41 –46
1991 - 2000