“It is characteristic of the Oxford school of criticism to understand these [metaphysical] fallacies as logical non sequiturs—as though philosophers throughout the centuries had been, for reasons unknown, just a bit too stupid to discover the elementary flaws in their arguments. The truth of the matter is that elementary logical mistakes are quite rare in the history of philosophy; what appear to be errors in logic to minds disencumbered of questions that have been uncritically dismissed as “meaningless” are usually caused by semblances, unavoidable for beings whose whole existence is determined by appearance. Hence, In our context the only relevant question is whether the semblances are inauthentic or authentic ones, whether they are caused by dogmatic beliefs and arbitrary assumptions, mere mirages that disappear upon closer inspection, or whether they are inherent in the paradoxical condition of a living being that, though itself part of the world of appearances, is in possession of a faculty, the ability to think, that permits the mind to withdraw from the world without ever being able to leave it or transcend it.”

2003-10-20
Mommie Dearest
Slate
1091-2339
http://www.slate.com/articles/news_and_politics/fighting_words/2003/10/mommie_dearest.html, quoted in Michael Shermer, "The Skeptic's Skeptic," Scientific American, November 2010, p. 86.
February/March
http://secularhumanism.org/library/fi/hitchens_24_2.html
Less than Miraculous
Free Inquiry
0272-0701
24
"What can be asserted without evidence can also be dismissed without evidence." appears by itself in God Is Not Great: How Religion Poisons Everything (2007).
Translation of the Latin phrase "Quod gratis asseritur, gratis negatur.".
2000s, 2003
Variant: "What can be asserted without proof can be dismissed without proof." in * 2004

Source: Mathematics and Humor: A Study of the Logic of Humor (1980), Chapter 2, “Axioms, Levels, and Iteration” (p. 19)

Source: A Dictionary of Thoughts, 1891, p. 26.

This statement refers to a koan
Gödel, Escher, Bach: an Eternal Golden Braid (1979)

Confessions Of A Sceptic
The Nemesis of Faith (1849)
Context: Happily I had very early learned the fallacy of building much on logic and verbal argument. Single sets of truths I knew to be as little conclusive in theology as in physics; and, in one as in the other, no theory to be worth anything, however plausibly backed up with Scripture texts or facts, which was not gathered bona fide from the analysis of all the attainable phenomena, and verified wherever possible by experiment.
"Here is a theory of the world which you bring for my acceptance: well, there is the world; try — will the key fit? can you read the language into sense by it?" was the only method; and so I was led always to look at broad results, at pages and chapters, rather than at single words and sentences, where for a few lines a false key may serve to make a meaning. So of these broad observations I only expected a broad solution.

Source: Dreams of a Final Theory

Source: The Dark Tower

Source: Soul Mountain (1989), ch. 8, p. 50