Nearly two centuries before "evidence-based medicine" became a slogan, a London farrier named John Hinds wrote a preface that reads like a manifesto against what we would today call cargo-cult practice. In his 1827 treatise on horse diseases, Hinds warned readers not to trust the fashionable recipe books of his day — including, presumably, his own — unless they first understood why a remedy worked.

Indeed, he should study it hard, if he would become proficient in "the Art of Farriery," and not rely implicitly upon other people's prescriptions for the cure of any alleged disorder, which have been composed for the most part without any such preparation. From this neglect, also, symptoms of one disorder are confounded with those of another, when the proposed remedies cannot possibly effect the cure.

His prescription for genuine competence was startlingly direct: cut open dead horses. Whenever, and wherever, you can.

He had best to comply with the advice strenuously urged at the very outset, to examine the internal parts of dead horses, as often as opportunity presents itself, which in the neighbourhood of large towns and hunts is frequent enough. For this is the manner in which I was myself mainly instructed.

What's remarkable here is not the recommendation of dissection — anatomists had been doing it for centuries — but Hinds's insistence that the working farrier, the ordinary shoeing-smith or groom, had a moral obligation to develop his own diagnostic eye rather than mechanically match symptoms to recipes in a book. He was writing at the very moment veterinary medicine was professionalizing (the Royal Veterinary College had opened in 1791), and the market was flooded with "quack" pamphlets promising cures. His response was to tell readers, in effect: your book is only as good as your ability to see through it.

Modern medicine has spent the past thirty years rediscovering the same tension. Clinical decision-support systems, protocol-driven care, and now large language models can all produce a plausible answer for any set of symptoms. But study after study finds that the practitioners who catch the outliers — the atypical presentations, the two-diseases-at-once cases — are the ones who understand pathophysiology deeply enough to distrust the pattern-match. Physicians call this the difference between "System 1" and "System 2" thinking. Hinds called it the difference between studying nature and copying prescriptions.

His observation that "symptoms of one disorder are confounded with those of another" when the remedy is applied without understanding is essentially a description of diagnostic anchoring bias, first named in the medical literature in the 1970s. Hinds had no framework for cognitive bias. He just watched a lot of horses die from correctly-applied wrong cures.

The advice to walk down to the knacker's yard and open up a corpse is quaint. The underlying claim — that reading recipes is not the same as understanding disease — is not.