It's not sufficiently recognized, but because Clifford's arguments in "The Ethics of Belief" (PDF) are ethical, tout court, they have direct implications for a much wider field of human life than just inquiry and belief. The argument cannot be confined just to belief. An obvious case is the common property argument:
And no one man’s belief is in any case a private matter which concerns himself alone. Our lives are guided by that general conception of the course of things which has been created by society for social purposes. Our words, our phrases, our forms and processes and modes of thought, are common property, fashioned and perfected from age to age; an heirloom which every succeeding generation inherits as a precious deposit and a sacred trust to be handled on to the next one, not unchanged but enlarged and purified, with some clear marks of its proper handiwork. Into this, for good or ill, is woven every belief of every man who has speech of his fellows. An awful privilege, and an awful responsibility, that we should help to create the world in which posterity will live.
It follows directly from this (if it works as it is supposed to work) that it is always wrong to lie, since by lying you are contaminating the 'precious deposit' by affecting the beliefs of others by communication. But more than this, it seems to require us to take a stronger stance than is taken even by very strong positions against lying, namely, that any kind of deception whatsoever is morally wrong, because you are interfering with the ability of others to believe well.
This is perhaps not surprising, since one of Clifford's arguments is that believing without evidence is wrong because it creates a dishonest society:
Habitual want of care about what I believe leads to habitual want of care in others about the truth of what is told to me. Men speak the truth to one another when each reveres the truth in his own mind and in the other’s mind; but how shall my friend revere the truth in my mind when I myself am careless about it, when I believe thing because I want to believe them, and because they are comforting and pleasant? Will he not learn to cry, “Peace,” to me, when there is no peace? By such a course I shall surround myself with a thick atmosphere of falsehood and fraud, and in that I must live. It may matter little to me, in my cloud-castle of sweet illusions and darling lies; but it matters much to Man that I have made my neighbours ready to deceive.
Anyone who accepts Clifford's argument for the conclusion that 'it is wrong always, everywhere, and for everyone to believe anything upon insufficient evidence' is thereby committed to its being wrong always, everywhere, and for everyone to do something that will deceive or mislead someone else.
This, of course, is not the same as to say that everyone who accepts the claim is so committed; it's Clifford's argument for it in particular that, built entirely on moral principles, requires that those moral principles be applied with parity and consistency across the board. Not every kind of 'ethics of belief' is moralizing the way Clifford's is; William James in "The Will to Believe", for instance, relativizes the kind of 'ethics of belief' you use to the specific goals you have in inquiry, and so is (perhaps unsurprisingly) more accurately called a 'pragmatics of belief' than an 'ethics of belief'.
The fundamental problem with Clifford's argument on this point, of course, is that it's simply wrong, when we look at the evidence, to say that every single belief, without exception, harms the 'precious deposit' or contributes to more dishonest society; this posits a fragility in human society that simply does not show up when you look at how societies work. Every human society has to deal with falsehoods by the load; there is no way to avoid that, because even in the best of times people will make honest mistakes, be confronted with misleading evidence through no fault of their own, misinterpret and misread evidence, and the like. Societies develop means for dealing with it; they adapt and move on. Nor does there seem to be any evidence that a society in which some people occasionally show a disregard for truth is a society that slides into being one in which people in general are "ready to deceive". A lot of things have to go into habitual deception; merely coming into contact with disregard for truth does not seem to give us a cause proportionate to the purported effect. And we see the same with lying: most lies in fact seem to be swamped out or neutralized, and doing things that mislead others does not seem to be particularly likely to make them liars.
The real problem with lying, of course, is that it is a perversion of the natural ends of reason as communicative. But it is true that deliberately saying what you know to be false is a sin against trust as part of common good. It's just not necessarily a sin that on its own damages that common good, and society is not so fragile as to be corrupted by occasional wrongdoing. And neither of the arguments against lying suggests that everything you do that could deceive and mislead is always wrong; although you may generally have to be careful.
The perversion account of lying is usually the most anti-lying position on the table these days (it is often vehemently attacked for being too strong); but Clifford as a nineteenth-century Englishman in a culture in which 'candour' was considered a national virtue and candid behavior and honesty a mark of a civilized gentleman, and John Henry Newman had been attacked for dishonesty just a little over a decade before simply for suggesting that it was sometimes moral to be cautious in expressing the truth. Clifford could assume at the time that it was not a point at which most of his audience would have pressed his argument.
Various Links of Interest
* This has been going around Twitter due to Nick Kapur: A Japanese illustrated history of the United States from 1861. It hits the major highlights: Columbus, the American Revolution, John Adams slaying a giant serpent with a sword, George Washington punching a tiger, John Adams killing another giant serpent with the help of a giant eagle, all the key moments of American history. The book in question is Osanaetoki Bankokubanashi by Nozaki Bunzō under the pseudonym Kanagaki Robun (writer) and Utagawa Yoshitora (illustrator).
* Adrian Currie on the paleontologist Mary Anning
* Corey Dethier, William Whewell's Semantic Account of Induction (PDF)
* Nathanael Blake, Living With Morals: A Review of The Fall of Gondolin
* Juhana Toivanen, The Fate of the Flying Man: Medieval Reception of Avicenna's Thought Experiment
* Timothy Chow, The Consistency of Arithmetic (PDF)
* Given some complaints that are being made about politics today, it's worth remembering Thea Skocpol's argument from over a decade ago: The Narrowing of Civic Life.
Flann O'Brien, The Third Policeman
Simon Conway Morris, Life's Solution: Inevitable Humans in a Lonely Universe
C. S. Lewis, On Stories
Jules Verne, The Survivors of the Chancellor