Jump to ContentJump to Main Navigation
How We Reason$
Users without a subscription are not able to see the full content.

Philip Johnson-Laird

Print publication date: 2008

Print ISBN-13: 9780199551330

Published to Oxford Scholarship Online: March 2012

DOI: 10.1093/acprof:oso/9780199551330.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (www.oxfordscholarship.com). (c) Copyright Oxford University Press, 2018. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a monograph in OSO for personal use (for details see http://www.oxfordscholarship.com/page/privacy-policy).date: 17 July 2018

Unwrapping an Enigma

Unwrapping an Enigma

Chapter:
(p.387) Chapter 26 Unwrapping an Enigma
Source:
How We Reason
Author(s):

Philip N. Johnson-Laird

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780199551330.003.0026

This chapter begins by describing the ciphers and the Enigma machine, and the German protocol for setting up the machine for encoding or decoding a message. It was here that they made one fateful error. And then the chapter explores Gordon Welchman's thinking as he broke the code. The Enigma machine had two separate components that created its encodings. Welchman described his thinking in a sequence of steps. These steps are discussed in detail. Each step in Welchman's reasoning can be explained in terms of the major processes of deductive and inductive reasoning that the model theory elucidates. His principal inductions are based on observations of the output of machines. The initial cracking of the Enigma code, which Welchman duplicated, occurred at the same time that other methods for breaking it were under development.

Keywords:   Enigma machine, German protocol, Gordon Welchman, thinking, reasoning, model theory, Enigma code

Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter.

Please, subscribe or login to access full text content.

If you think you should have access to this title, please contact your librarian.

To troubleshoot, please check our FAQs , and if you can't find the answer there, please contact us .