Answer to Dr. Priestley's Letters to a Philosophical Unbeliever

In Short

This book serves as a deliberate, polemical riposte to Joseph Priestley’s Letters to a Philosophical Unbeliever. Through a series of logical dissections, the author rejects the notion that a supreme, intelligent designer is necessary to explain the existence of the universe. By shifting the burden of proof back onto those who claim a deity exists, the text argues for a materialist view of nature. It has endured as a significant primary source for the history of free thought, capturing the intellectual tension between eighteenth-century theology and the emerging courage of early secular skepticism.

The Story

The narrative arc of the book is defined by the steady, systematic dismantling of a theological worldview. It begins with the author—writing under the pseudonym William Hammon—accepting the public invitation of the theologian Joseph Priestley to debate the existence of God. The author immediately establishes his position: he does not seek to be a martyr, but he refuses to be silenced by the “tyranny” of ecclesiastics who label critical inquiry as disgraceful. He posits that if religion were truly based on reason, it would welcome debate rather than fear it.

As the argument progresses, the author examines the core pillars of natural religion. He rejects the "cosmological argument," which suggests that every effect must have a cause, by questioning why the chain of causality must end at an invisible, infinite deity rather than in the material world itself. He challenges the notion that the universe exhibits a "unity of design," suggesting instead that if we must infer a cause for everything we see, there is no logical reason to stop at one god; a plurality of creators would be just as plausible, if not more so, given the complexities of nature.

Moving into the realm of morality, the author addresses the common fear that a society without a god would descend into chaos. He argues that morality is not a divine byproduct but a social necessity, suggesting that religion itself often acts as a cloak for immorality by promising easy absolution. He contrasts the "debased" state of the fearful believer—who bows to a phantom—with the "dignity" of the atheist, who views himself as a vital link in the grand, eternal chain of nature.

The argument then turns to the specific contradictions in Priestley’s own logic. The author catalogues a series of "false assertions" and "absurdities" found in Priestley's work, ranging from the nature of infinite space to the definition of benevolence. He points out that if a deity is meant to be perfectly good and all-powerful, the presence of widespread suffering remains an irreconcilable problem—one that theologians attempt to solve with "romantic hopes" of a future life, which, he argues, lack any empirical foundation.

The book concludes with a poignant, unanswered postscript: a private letter sent to Priestley before publication. In it, the author expresses the very real fear of social and legal persecution for his views, asking for assurance that a "poor atheist" might speak his mind without facing the pillory. Receiving no reply, the author publishes his challenge, leaving his arguments to stand in the silence of his opponent, effectively shifting the status of the debate from a private dialogue to a bold, public declaration of independence from traditional faith.

How It Unfolds

The challenge accepted The author opens by asserting that free thought is a virtue, not a vice, and that ecclesiastics act as tyrants when they demand reason be used to support faith while simultaneously damning those who question it. He accepts the invitation to debate, insisting that he will treat the subject with the same rigor as any other scientific inquiry.

The materialist alternative Moving to the nature of existence, the author posits that the universe is self-existent and eternal, requiring no external, "extraneous" force to account for its properties. He defines his "deity" as the natural, intelligent principle inherent in matter itself, rejecting the idea of a machine-maker existing outside the machine.

The moral critique The author tackles the question of whether an atheist can be a moral citizen, arguing that honesty and social cohesion do not rely on the fear of a divine judge. He suggests that religious belief often encourages vice by offering a path to forgiveness, whereas the atheist feels a deeper responsibility to the real world.

The logical dissection The final portion of the work provides a categorized list of Priestley’s perceived logical errors, exposing the contradictions in how theologians define attributes like infinity, ubiquity, and benevolence. By highlighting these tensions, the author argues that the entire structure of natural religion collapses under the weight of its own inconsistencies.

The People

The book primarily features the author, William Hammon, and his interlocutor, Joseph Priestley. Hammon presents himself as a man of reason—a “Philosophical Unbeliever” who possesses no desire for religious conversion or personal fame, but who feels a deep, ethical obligation to speak truth to power. He is methodical, slightly weary of the risks he faces, and fiercely committed to the idea that a mind should be kept “sane” by refusing to believe anything that contradicts empirical experience.

Joseph Priestley is the intellectual foil. As a prominent theologian and philosopher, he represents the educated religious establishment. He is portrayed not as a villain, but as a man of “candor” whose own intellectual rigor has inadvertently provided the tools for his critique. While the author admires Priestley’s willingness to debate, he is frustrated by what he views as Priestley’s failure to follow his own logical arguments to their inevitable conclusions. Priestley remains a silent figure in the text—represented only by his previous writings and his lack of a reply—serving as the embodiment of the theological position that the author aims to dismantle.

In Its Own Voice

Regarding the suppression of ideas by religious authorities, the author observes:

"They invite us to the argument, yet damn us to eternal punishment for the use of reason on the subject."

Describing the origin of belief in a deity, he notes:

"In fear lies the origin of all fancied deities, whether sole or numberless."

Reflecting on his own identity as a thinker, he writes:

"My mind (I was going to say, thank God) is sane at present, and I intend to keep it so."

What It's Really About

At its core, this book is an inquiry into the limits of reason and the definition of truth. It asks whether the universe can be understood as a closed, material system governed by its own inherent laws, or if it necessarily requires a transcendent agent. The author explores the psychological roots of religion, positing that it is born of fear and maintained through habit, while asserting that genuine morality is a human construct, independent of supernatural sanction. Ultimately, the work is a defense of intellectual autonomy, arguing that if truth is to be found, it must be sought through rigorous questioning, regardless of the social or ecclesiastical cost.

Why Read It Today

Readers with an interest in the history of ideas, particularly the intellectual ferment of the Enlightenment, will find this a fascinating document. It offers a rare, direct look at the early arguments for secularism, stripped of the centuries of consensus that followed. The prose is distinctively eighteenth-century—formal, measured, and intellectually aggressive—providing a window into a time when simply questioning the existence of a deity was a dangerous act of public defiance.

The book is not without its difficulties; the reader must navigate the archaic, idiosyncratic punctuation and spelling of the 1782 edition, which can require a slower, more deliberate pace. Furthermore, the reliance on specific theological texts of the era means that some of the finer points of the debate may feel removed from modern discourse. However, there is a visceral, human quality to the author’s voice that transcends its period. You are reading the words of someone who is consciously choosing to place himself in the crosshairs of the law for the sake of his convictions. The courage of his stance, combined with his dry, sharp wit, makes it a compelling read for anyone who values the history of free speech and the evolution of the rationalist spirit.