An early modern commonplace book was a collection of excepted passages, or "commonplaces"--this meant quotations of universal applicability, not banal or hackneyed phrases--selected by a reader and arranged under general topic headings like "reputation" or "friendship." For example, the Elizabethan courtier Sir Francis Castillion extracted a passage from Philip Sidney's Arcadia (1590) on marriage and copied it into his commonplace book.
The idea was that readers could turn to their commonplace books as a repository of witty and apt phrases on a variety of subjects. But critics pointed out that seemingly learned people might simply crib all their knowledge from quotations: as Richard West wrote in 1638, "Their Braines lye all in Notes; Lord! How they’d looke / If they should chance to loose their Table-book!"
Another problem with the commonplace book was that the system of topic headings was not infallible: in a commonplace book kept in the 1650s by Robert Southwell, later president of the Royal Society, some headings are left blank (Academia, Oratio, Somia, Tedium), while others clearly require more than one page (Authoritas, Deus, Error, Religio). When he isn’t cramming more notes in an impossibly small hand at the bottom of the page, Southwell’s solution is to cross out existing commonplace headings and replace them with the topics for which he has more material.
Indeed, archival evidence suggests that in practice commonplacers rarely followed the established templates for making a commonplace book. An early seventeenth-century reader named William Hill, for example, filled his notebook with ink recipes, handwriting specimens, and other heterogeneous content: in just one leaf of the manuscript, we find both a sobering commonplace--"Death is not partiall because an equal law it makes for all men"--and a recipe "to make greene letters."
And perhaps most troublingly, there was an uncertain correlation between a voluminous commonplace book and actual reading. For example, Francis Meres's printed commonplace book Palladis Tamia (1598) is best known as the first reference to Shakespeare in print, but also contains brief allusions to innumerable other authors, titles, and quotations--familiar names like Marlowe and Jonson, but also nonentities like "the famous Dr. Leg of Cambridge."
For some commentators, such exhaustive compilations were evasions of reading rather than aids to it. In Micro-cosmographie (1628), John Earle mocked a "pretender to learning" who is "a great Nomen-clator of Authors, which he has read in generall in the Catalogue, and in particular in the Title, and goes seldom so farre as the Dedication." In a jab at collections like Palladis Tamia, Earle suggests that merely knowing the names of authors--and some choice quotes from their books--is no substitute for actually reading them.