In 1919, Newton's theory fell to Einstein's general theory of relativity. In the late 1920s, the logical positivists rejected Kant's synthetic "a priori" and asserted Hume's fork, so called, while hinging it at language—the analytic/synthetic division—while presuming that by holding to analyticity, they could develop a logical syntax entailing both necessity and aprioricity via logic on side and, on the other side, demand empirical verification, altogether restricting philosophical discourse to claims verifiable as either false or true. In the early 1950s, Willard Van Orman Quine undermined the analytic/synthetic division by explicating ontological relativity, as every term in any statement has its meaning contingent on a vast network of knowledge and belief, the speaker's conception of the entire world. By the early 1970s, Saul Kripke established the necessary "a posteriori", since if the Morning Star and the Evening Star are the same star, they are the same star by necessity, but this is known true by a human only through relevant experience.