him. For Leo Strauss, philosophers' texts offered the reader lucid "exoteric" (salutary) and obscure "esoteric" (true) teachings, which are concealed to the reader of ordinary intellect; emphasizing that writers often left contradictions and other errors to encourage the reader's more scrupulous (re-)reading of the text. In observing and maintaining the "exoteric—esoteric" dichotomy, Strauss was accused of obscurantism, and for writing esoterically. Bill Joy In the Wired magazine article "Why the Future Doesn't Need Us" (April 2000), the computer scientist Bill Joy, then a Sun Microsystems chief scientist, in the sub-title proposed that: "Our most powerful twenty-first-century technologies—robotics, genetic engineering, and nanotech[nology]—are threatening to make humans an endangered species"; in the body, he posits that: Joy's proposal for limiting the dissemination of "certain" knowledge, in behalf of preserving society, was quickly likened to obscurantism. A year later, the American Association for the Advancement of Science, in the Science and Technology Policy Yearbook 2001, published the article "A Response to Bill Joy and the Doom-and-Gloom Technofuturists", wherein the computer scientists John Seely Brown and Paul Duguid countered his proposal as technological tunnel vision, and the predicted technologically derived problems as infeasible, for disregarding the influence of non-scientists upon such societal problems. Appeal to emotion In the essay "Why I Am Not a Conservative" (1960), the economist Friedrich von Hayek said that political conservatism is ideologically unrealistic, because of the conservative person's inability to adapt to changing human realities and refusal to offer a positive political program that benefits everyone in a society. In that context, Hayek used the term obscurantism differently, to denote and describe the denial of the empirical truth of scientific theory, because of the disagreeable moral consequences that might arise from acceptance of fact. Deliberate obscurity The second sense of obscurantism denotes making knowledge abstruse, that is, difficult to grasp. In the 19th and 20th centuries obscurantism became a polemical term for accusing an author of deliberately writing obscurely, in order to hide his or her intellectual vacuousness. Philosophers who are neither empiricists nor positivists often are considered obscurantists when describing the abstract concepts of their disciplines. For philosophic reasons, such authors might modify or reject verifiability, falsifiability, and logical non-contradiction. From that perspective, obscure (clouded, vague, abstruse) writing does not necessarily indicate that the writer has a poor grasp of the subject, because unintelligible writing sometimes is purposeful and philosophically considered. Aristotle Aristotle divided his own works into