T F F T T T T (4) And (5) are not incompatible. That’s Joe’s error. A logical experiment On the way, Joe was claiming that Carr was necessarily in the shop. Suppose Joe and Jim arrived at the shop. Question: What does the actual presence or absence of Carr teach Joe about his claim? Case 1: Carr was in the shop. It confirms but does not prove Joe’s claim. Case 2: Carr was not in the shop. It disconfirms and disproves Joe’s claim. Confirmation and disconfirmation reasoning as essential in scientific method. ----------------------------------------------------------------------------------------------------------------------------------- Conditions When we say that A is a condition for B, three meanings are possible: 1. A is a Sufficient condition for B. The occurence of A requires the occurence of B Ex. Being in Tallinn is a sufficient condition for being in Estonia
visualize the devilish grin of the inventor as he finishes enciphering the message, and thinks, "They'll never get that!" The inventors fall into two categories. One type has just read Edgar Allan Poe's dictum in "The Gold-Bug" that "it may well be doubted whether human ingenuity can construct an enigma of the kind which human ingenuity may not, by proper application, resolve," and has, in half an hour, invented an unbreakable cipher that disproves it. The other has just devised a cipher so simple that a 12-year-old can operate it (never a 13-year-old), and as a patriotic American is giving it to his government for a mere $100,000—a cheap price for assuring the security of information worth much more than that. Few of the inventors have any idea of the volume of modern communications, of the conditions under which ciphering is done, of modern cryptanalysis, or that the unbreakable cipher, in the form of the
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