“There is a popular superstition that "realism" asserts itself in the cataloguing of a great number of material objects, in explaining mechanical processes, the methods of operating manufactories and trades, and in minutely and unsparingly describing physical sensations. But is not realism, more than it is anything else, an attitude of mind on the part of the writer toward his material, a vague indication of the sympathy and candour with which he accepts, rather than chooses, his theme?”

The Romance of Commerce (1918), A Representative Business of the Twentieth Century

This material is always contaminated by principles which he does not know and which, if known, would be extremely hard to test.
Pg. 66.
Against Method (1975)

Quote of Malevich, cited in Artists on Art; from the 14th – 20th centuries, ed. Robert Goldwater and Marco Treves; Pantheon Books, 1972, London, p. 452
1910 - 1920

An Inquiry into Meaning and Truth (1940), Introduction, p. 15
1940s
Context: Science seems to be at war with itself.... Naive realism leads to physics, and physics, if true, shows naive realism to be false. Therefore naive realism, if true, is false; therefore it is false.

Materialism and Empirio-Criticism (1908)

Source: Psyche and Matter (1992), p. 208

Part 1, Book 1, ch. 2, sect. 7.
Philosophy of the Inductive Sciences (1840)

William Dean Howells, Criticism and Fiction (1891), Chapter 15

Source: Rudolf Steiner: The Man and His Vision (1985), p. 166