Descartes's Secret Notebook

René Descartes (1596–1650) is one of the towering and central figures in Western philosophy and mathematics. His apothegm “Cogito, ergo sum” marked the birth of the mind-body problem, while his creation of so-called Cartesian coordinates have made our physical and intellectual conquest of physical space possible.

But Descartes had a mysterious and mystical side, as well. Almost certainly a member of the occult brotherhood of the Rosicrucians, he kept a secret notebook, now lost, most of which was written in code. After Descartes’s death, Gottfried Leibniz, inventor of calculus and one of the greatest mathematicians in history, moved to Paris in search of this notebook—and eventually found it in the possession of Claude Clerselier, a friend of Descartes. Leibniz called on Clerselier and was allowed to copy only a couple of pages—which, though written in code, he amazingly deciphered there on the spot. Leibniz’s hastily scribbled notes are all we have today of Descartes’s notebook, which has disappeared.

Why did Descartes keep a secret notebook, and what were its contents? The answers to these questions lead Amir Aczel and the reader on an exciting, swashbuckling journey, and offer a fascinating look at one of the great figures of Western culture.

Standard and Primary covers are widely available through general retailers. They often have higher print runs and can be cheaper, especially during sales.

In contrast, Direct Market (DM) and variant covers are primarily sold in comic shops. DM editions tend to have more limited availability and may be more valuable to collectors.

The main differences lie in artwork style, availability, price, and collector appeal. Ultimately, the choice between standard and variant covers depends on personal preference, budget, and individual collecting goals.

Comic book enthusiasts have various formats to choose from when collecting their favorite stories.
Here's a brief overview of the main types:

Omnibus

• Large, hardcover collections
• Usually contain complete runs or extensive story arcs
• Typically 800-1000+ pages
• Higher price point, often €100-€150

Oversized Hardcover (OHC)

• Similar dimensions to omnibus, but thinner
• Collect shorter runs or story arcs
• Usually 300-600 pages
• Priced between €30-€50

Hardcover (HC)

• Standard-sized hardcover books
• Collect 6-12 issues typically
• Similar dimensions to single issues, but with a hard cover
• Priced around €25-€35

Trade Paperback (TP)

• Softcover collections
• Standard comic book size
• Usually collect 4-6 issues
• Most affordable option, typically €15-€25

Other Formats

• Absolute Editions: Oversized, deluxe hardcovers (mainly DC Comics)
• Compendiums: Massive paperback collections
• Graphic Novels (OGN/GN): Original stories not previously released as single issues

The choice between these formats often depends on personal preference, budget, and collecting goals. Omnibus and OHC editions offer larger artwork and more content but at a higher price, while TPs provide a more affordable way to collect complete story arcs