“The confidence people have in their beliefs is not a measure of the quality of evidence but of the coherence of the story that the mind has managed to construct,” Nobel-winning psychologist Daniel Kahneman observed in summarizing his pioneering behavioral psychology studies of how and why our minds mislead us. And yet our beliefs are the compass by which we navigate the landscape of reality, steering our actions and thus shaping our impact on that very reality. The great physicist David Bohm captured this inescapable dependency memorably: “Reality is what we take to be true. What we take to be true is what we believe… What we believe determines what we take to be true.”

How, then, do we align our beliefs with truth rather than illusion, so that we may perceive the most accurate representation of reality of which the human mind is capable, in turn guiding our actions toward noble and constructive ends?

That’s what the English mathematician and philosopher William Kingdon Clifford (May 4, 1845–March 3, 1879) explored with uncommon insight and rhetorical elegance nearly a century and a half before the golden age of “alternative facts.”

By the time tuberculosis claimed his life at the unjust age of thirty-three, Clifford had revolutionized mathematics by developing geometric algebra, had written a book of fairy tales for children, and had become the first person to suggest that gravity might be a function of an underlying cosmic geometry, developing what he called a “space-theory of matter” decades before Einstein transformed our understanding of the universe by bridging space and time into a geometry of spacetime.

But one of Clifford’s most lasting contributions is an essay titled “The Ethics of Belief,” originally published in an 1877 issue of the journal Contemporary Review and later included in Reason and Responsibility: Readings in Some Basic Problems of Philosophy (public library). In it, Clifford probes the nature of right and wrong, the infernal abyss between belief and truth, and our responsibility to the truth despite our habitual human deviations into unreason, delusion, and rationalization.

Clifford, at only thirty-two, begins with a parable containing an ethical thought experiment:

A shipowner was about to send to sea an emigrant-ship. He knew that she was old, and not overwell built at the first; that she had seen many seas and climes, and often had needed repairs. Doubts had been suggested to him that possibly she was not seaworthy. These doubts preyed upon his mind, and made him unhappy; he thought that perhaps he ought to have her thoroughly overhauled and refitted, even though this should put him at great expense. Before the ship sailed, however, he succeeded in overcoming these melancholy reflections. He said to himself that she had gone safely through so many voyages and weathered so many storms that it was idle to suppose she would not come safely home from this trip also. He would put his trust in Providence, which could hardly fail to protect all these unhappy families that were leaving their fatherland to seek for better times elsewhere. He would dismiss from his mind all ungenerous suspicions about the honesty of builders and contractors. In such ways he acquired a sincere and comfortable conviction that his vessel was thoroughly safe and seaworthy; he watched her departure with a light heart, and benevolent wishes for the success of the exiles in their strange new home that was to be; and he got his insurance-money when she went down in mid-ocean and told no tales.

What shall we say of him? Surely this, that he was verily guilty of the death of those men. It is admitted that he did sincerely believe in the soundness of his ship; but the sincerity of his conviction can in no wise help him, because he had no right to believe on such evidence as was before him. He had acquired his belief not by honestly earning it in patient investigation, but by stifling his doubts. And although in the end he may have felt so sure about it that he could not think otherwise, yet inasmuch as he had knowingly and willingly worked himself into that frame of mind, he must be held responsible for it.

Clifford adds a layer of ethical complexity by arguing that even if the ship hadn’t sunk, the shipowner would be guilty of the same error of judgment, for he “would not have been innocent, he would only have been not found out.” He writes:

The question of right or wrong has to do with the origin of his belief, not the matter of it; not what it was, but how he got it; not whether it turned out to be true or false, but whether he had a right to believe on such evidence as was before him.

[…]

For it is not possible so to sever the belief from the action it suggests as to condemn the one without condemning the other. No man holding a strong belief on one side of a question, or even wishing to hold a belief on one side, can investigate it with such fairness and completeness as if he were really in doubt and unbiased; so that the existence of a belief not founded on fair inquiry unfits a man for the performance of this necessary duty.

A century before psychologists came to identify such cognitive flaws as confirmation bias and the backfire effect, Clifford adds:

Nor is it that truly a belief at all which has not some influence upon the actions of him who holds it. He who truly believes that which prompts him to an action has looked upon the action to lust after it, he has committed it already in his heart. If a belief is not realized immediately in open deeds, it is stored up for the guidance of the future. It goes to make a part of that aggregate of beliefs which is the link between sensation and action at every moment of all our lives, and which is so organized and compacted together that no part of it can be isolated from the rest, but every new addition modifies the structure of the whole. No real belief, however trifling and fragmentary it may seem, is ever truly insignificant; it prepares us to receive more of its like, confirms those which resembled it before, and weakens others; and so gradually it lays a stealthy train in our inmost thoughts, which may someday explode into overt action, and leave its stamp upon our character for ever.

In a sentiment evocative of the Indian poet and philosopher Tagore’s reflections on the interdependence of existence, Clifford takes care to highlight the sociological tapestry out of which each strand of our private beliefs is frayed:

No one man’s belief is in any case a private matter which concerns himself alone. Our lives our 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. A awful privilege, and an awful responsibility, that we should help to create the world in which posterity will live.

In a passage of astounding pertinence today, as dangerous ideologies divorced from truth offer false comfort in “alternative facts” to the detriment of our common good, Clifford cautions:

Belief, that sacred faculty which prompts the decisions of our will, and knits into harmonious working all the compacted energies of our being, is ours not for ourselves but for humanity. It is rightly used on truths which have been established by long experience and waiting toil, and which have stood in the fierce light of free and fearless questioning. Then it helps to bind men together, and to strengthen and direct their common action. It is desecrated when given to unproved and unquestioned statements, for the solace and private pleasure of the believer; to add a tinsel splendour to the plain straight road of our life and display a bright mirage beyond it; or even to drown the common sorrows of our kind by a self-deception which allows them not only to cast down, but also to degrade us. Whoso would deserve well of his fellows in this matter will guard the purity of his beliefs with a very fanaticism of jealous care, lest at any time it should rest on an unworthy object, and catch a stain which can never be wiped away.

Three centuries after Western philosophy founding father and reason crusader René Descartes asserted that “it is not enough to have a good mind; the main thing is to apply it well,” Clifford adds:

In regard, then, to the sacred tradition of humanity, we learn that it consists, not in propositions or statements which are to be accepted and believed on the authority of the tradition, but in questions rightly asked, in conceptions which enable us to ask further questions, and in methods of answering questions. The value of all these things depends on their being tested day by day. The very sacredness of the precious deposit imposes upon us the duty and the responsibility of testing it, of purifying and enlarging it to the utmost of our power. He who makes use of its results to stifle his own doubts, or to hamper the inquiry of others, is guilty of sacrilege which centuries shall never be able to blot out.

How to purify and enlarge our access to truth is what Carl Sagan outlined a century later in his timeless Baloney Detection Kit, but Clifford himself crystallizes the most effective approach in a wonderfully succinct dictum:

It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.

Complement with Lewis Thomas, one of the most enchanting writers of the past century, on the transmutation of ignorance into truth, Karl Popper on the crucial difference between truth and certainty, and Laura (Riding) Jackson’s unusual and profound 1967 manifesto for the telling of truth.