<b>Transcriber’s notes</b>: The text of this book has been preserved as closely as practicable to its original form. However, the author used some unusual symbols, and I have taken the liberty of using Unicode characters with similar appearance (ꖌ ᔕ) as substitutes, disregarding their official meaning and aware that they might not display on all devices. An archaic symbol used by the author to indicate the mathematical ‘factorial’ function has been replaced by the modern equivalent, viz. ! Unusual placements of various sub- and superscripted symbols remain as in the original text. In this plain-text version, italic text is denoted by *asterisks*; superscripted and subscripted characters are enclosed within {curly} brackets preceded by a caret (^) or underline (_) respectively. Inconsistencies of punctuation have been corrected silently, but inconsistent spellings such as *Roemer, Römer, Rœmer* have not been altered. A list of corrected spellings is appended at the end of the book. Footnotes have been renumbered consecutively and positioned below the relevant paragraphs. A missing footnote marker has been inserted on p.751 after tracking down the original document. A missing negative symbol has been added to an exponent in a formula on p.327. There is a misleading calculation on p.194 and the table that follows, regarding progressive powers of two: ((2^{2})^{2})^{2} is equivalent to (16)^{2} which equals 256 not 65,356 as stated, but 2^{16} does equal 65,356. [sic] has been inserted on p.179 alongside a statement that the alphabet contains 24 letters; however, the statement may well be correct given that it was written in 1704 by a Flemish author and the language is not specified. A large arithmetic triangle on p.184 cannot be displayed optimally in this plain-text version for lack of space THE PRINCIPLES OF SCIENCE. [Illustration] [Illustration: THE LOGICAL MACHINE.] THE PRINCIPLES OF SCIENCE: *A TREATISE ON LOGIC* *AND* *SCIENTIFIC METHOD.* BY W. STANLEY JEVONS, LL.D. (EDINB.), M.A. (LOND.), F.R.S. London: MACMILLAN AND CO. 1883. *The Right of Translation and Reproduction is Reserved.* LONDON: R. Clay, Sons, & Taylor, Printers, BREAD STREET HILL. Stereotyped Edition. PREFACE *TO THE FIRST EDITION*.