Siris: A Chain of Philosophical Reflexions and Inquiries Concerning the Virtues of Tar Water

The central argument is a Neoplatonic ascent: tar-water's observed medicinal virtues point to a subtle, active principle—aether or fire—that pervades the natural world, and reflection on this principle leads the mind upward to God as the ultimate cause. Berkeley begins with tar-water not as a digression but as the first link in the chain: the healing properties of a humble remedy demonstrate the interconnectedness of natural causes and invite inquiry into their source . Recent scholarship argues that the entire work is organized by Neoplatonic metaphysics, and that Berkeley is disingenuous when he presents it as a casual chain of reflections . The physical and the metaphysical are continuous, not separate domains.

Siris applies immaterialism rather than restating it. Berkeley treats physical causes—including the aether or fire he invokes to explain tar-water's efficacy—as provisional hypotheses useful for natural philosophy, not as genuine causal agents in a materialist sense. The true causal agent is always God. As one study of the text notes, Berkeley distinguishes between the popular, mechanical language of natural philosophy and the proper metaphysical understanding of divine action . This allows him to engage seriously with contemporary chemistry and medicine without abandoning his earlier conviction that matter is an incoherent posit. The book shows immaterialism operating in a new register: not as a critique of substance but as a framework for integrating scientific inquiry with theological contemplation.

Siris was first published in Dublin in 1744, with a London reprint appearing the same year from W. Innys, C. Hitch, and C. Davis . It was Berkeley's most commercially successful work, going through multiple editions rapidly; one bibliography notes two Dublin and four London editions in its first year . A second edition, 'improved and corrected by the author,' was issued in 1744 . The work's popularity was driven partly by the contemporary enthusiasm for tar-water as a universal medicine, a reputation that faded in subsequent centuries. Modern scholarly editions treat Siris seriously as philosophy, but its initial reception was shaped as much by medical fashion as by metaphysical argument.

Siris is Berkeley's most explicitly Platonic work. Where the Principles and Three Dialogues argue from empiricist premises against material substance, Siris openly embraces ancient wisdom, the doctrine of ideas as innate in a Platonic sense, and the concept of a chain of being linking all created things to their source . Berkeley had always been sympathetic to Platonism, but in Siris he avows it without the rhetorical concessions to modern philosophy that marked his earlier writings. The style is also different: aphoristic, allusive, and organized around a progression rather than a sustained argument. This has led some readers to see it as a departure from his philosophical career, but recent scholarship emphasizes continuity—Siris extends his lifelong campaign against atheism into new territory .

A persistent misconception treats Siris as a curiosity or a symptom of Berkeley's decline into eccentricity, a book about tar-water with some mystical afterthoughts. This view is increasingly rejected by scholars. Carl O'Brien argues that Siris is 'frequently undervalued' and that a Neoplatonic key is required to make sense of it; the work's primary concerns reflect those of Berkeley's better-known writings, and reading it enacts the soul's ascent to God . Even the tar-water sections are integral: the healing properties of the remedy parallel the therapeutic function of ancient philosophy, which Berkeley enlists against atheism. The book is not a digression but a late, ambitious synthesis of his medical, scientific, and theological interests.

Contemporary reception was shaped by Berkeley's public identity as 'the good bishop' rather than as the abstract philosopher of immaterialism. His obituary in The Gentleman's Magazine remembered him as 'illustrious for his learning' and noted that he wrote 'a Treatise on Tar-Water, of which the effect is well remembered' . This reflects the eighteenth-century perception of Berkeley as a practical benefactor concerned with Ireland's welfare during years of famine and disease. The philosophical Berkeley and the philanthropic Berkeley were not yet separated in public consciousness. The irony is that the work now studied for its Neoplatonic metaphysics was valued in its own time primarily for its promise of a cheap, accessible medicine.