Old Book Hunter #4

Pothier is arguably the single most influential French legal mind of the 18th century — not because his own work was flashy, but because it was so systematic and clearly reasoned that it became the direct template for how French law got codified a generation later. When Napoleon's jurists sat down to draft the Code Civil, Pothier's treatises weren't background reading; they were working source material, lifted from almost verbatim in places. This particular treatise takes on a genuinely tricky legal category: aleatory contracts, meaning any agreement where the outcome depends on chance — insurance, annuities, and, directly, wagers. Pothier's inclusion of a dedicated treatise on gambling within this same legal framework is exactly the point: 18th-century law didn't yet have a clean way to separate "legitimate risk-sharing" from "a bet," and Pothier was one of the people doing the intellectual work of drawing that line. Two and a half centuries later, insurance law still runs on distinctions he helped articulate.

By the 1780s, insurance and gambling were not clearly separate things under English law, and that ambiguity had real consequences — people were taking out "insurance" policies on the lives of strangers, on the outcomes of wars, even on whether a particular ship would return, essentially placing bets dressed in legal language. Weskett's Complete Digest was one of the first serious attempts to systematically sort out what insurance actually was, as a matter of law, and what it wasn't. The book opens with an 80-page critical essay proposing reforms to correct what Weskett calls the "very great disorders" in how insurance was practiced, before moving into an alphabetically organized digest of the field as it then stood — citing, by name, the leading theorists of risk and probability of the age: Richard Cantillon, Malachy Postlethwayt, Abraham de Moivre, and Richard Price. That last name is worth sitting with for a second: Price was the actuary who, working from Bayesian principles, helped found the mathematical basis of modern life insurance. A book that puts Weskett's practical legal reforms in direct conversation with De Moivre and Price is a book standing exactly at the hinge between two histories that don't usually get told together — the history of probability as mathematics, and the history of insurance as law.

Philidor didn't just write a chess book — he invented modern positional chess theory. Before Philidor, chess strategy was largely about piece-by-piece tactical combinations; his famous line, "pawns are the soul of chess," reoriented the entire game around long-term structural planning. That reorientation stuck so completely that his name is still attached to specific openings and endgame positions taught to beginners today — "the Philidor Defense," "the Philidor Position." He was also, by all contemporary accounts, simply the best player in the world for decades, reportedly capable of playing multiple games blindfolded simultaneously, a feat considered nearly unbelievable at the time. This 1777 edition is Philidor's own expanded revision of his original 1749 text, meaning it reflects his mature thinking, not his first attempt — the book that a serious 18th-century player would actually have studied from.

Hoyle didn't just write rules down — he invented the entire genre of "the authoritative rulebook" for a game, and did it so thoroughly that his name became a common noun. "According to Hoyle" entered everyday English as shorthand for playing by the correct, official rules, a linguistic fossil of just how total his authority was in his own lifetime. Before Hoyle, card game rules were an oral, regional, constantly-disputed mess; after Hoyle, whist had a single, citable standard that clubs and private houses across England actually deferred to. His 1760 revision of the laws of whist remained the accepted standard for over a century, until a formal club finally superseded it in 1864. This volume bundles four of his treatises together — whist, quadrille, piquet, and backgammon — making it a genuine snapshot of exactly what educated 18th-century England was sitting down to play.

This is the book that turned "the mathematics of gambling" into "probability theory" as a formal discipline. De Moivre had presented an early version of the work to the Royal Society in 1711; by 1718 he'd expanded it into the first true textbook on the subject in English, dedicated to his close friend Isaac Newton. Within its pages are the first clear statements of ideas so foundational that most people who use them today have no idea they originated here — conditional probability, the multiplication rule for independent events, expectation itself as a formal concept. In a later edition, De Moivre would go on to derive an early form of what we now call the central limit theorem, one of the single most important results in all of statistics. Everything from actuarial science to modern risk modeling has a direct lineage back to this book — De Moivre and Edmund Halley are jointly credited as founders of the field of actuarial science itself. It's not an exaggeration to say this is the moment "gut feeling about luck" became "mathematics."