Summary: In a comprehensive critique dated July 27, 1923, Irving Fisher discusses revisions he would make to his book "The Making of Index Numbers." Primarily, the focus would be on differentiating between a ratio of averages and an average of ratios, with particular references to certain articles in 1923. Fisher expresses confidence in the core conclusions of the book, advocating for a stronger emphases on certain distinctions, like weighting in Appendix III. He addresses the circular test as unsound and weaker tests concerning index numbers, pinpointing the "time reversal" test as fundamentally important. Fisher reckons that many precise relationships exist within the study of index numbers, suggesting that despite its empirical and rational nature, it embodies the aspects of an exact science yet largely unexplored. Throughout the appendices, like Appendix VII, Fisher provides elaborate discussions and evaluations of different formulae, indicating the intricate calculations necessary to ensure accuracy within a fraction of 1%, making the book a critical addition to the understanding of index numbers.