It's a quote from Paul Halmos, he said that "The beginner should not be discouraged if he finds he does not have the prerequisites for reading the prerequisites."

What is the idea he tried to convey? Is it a reminder for the book authors to write self-contained book? Or is it an encouragement for beginners?

  • 5
    $\begingroup$ See the text preceding that for context, viz. "For the convenience of the reader, §0 is devoted to a detailed listing of exactly what knowledge is assumed in the various chapters. The beginner should be warned that some of the words and symbols in the latter part of §0 are defined only later, in the first seven chapters of the text, and that, accordingly, he should not be discouraged if, on first reading of §0, he finds that he does not have the prerequisites for reading the prerequisites." $\endgroup$ Apr 2, 2019 at 23:07
  • $\begingroup$ @BillDubuque Wonderful! Thanks! $\endgroup$
    – The R
    Apr 2, 2019 at 23:20
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    $\begingroup$ It is from the preface (p. v) of his book Measure Theory. $\endgroup$ Apr 2, 2019 at 23:21

1 Answer 1


Tertuliano Franco has one of the best interpretations for this quote I have seen, in the back cover of his soon to be released book on the Principles of Combinatorics and Probability. Here a snapshot

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The translation is more or less:

That is, studying mathematics is often a non-linear activity and prerequisites should not be taken literally.


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