Socio-economic empirical analysis must borrow mathematical tools, but only focusing on "mathematics" and ignoring the underlying "reason" of phenomena can easily lead to "hypothetical analysis", which formally meets the standards but loses the soul of quantitative research. This book emphasizes the eternal mission of scholars in the process of empirical analysis, which is to distinguish between "mathematics" and "reason", and to clarify the two entangled in phenomena. The first part is a systematic monograph, the second part is a reading note on the relationship between mathematics and reason, the third part is the "essay" of "one matter, one reason", and the fourth part is the author's early thinking on the relationship between mathematics and reason, which still serves as a warning to this day. As the fifth book of "Criticism Series of Contemporary Economic Statistics", it applies to the same audience as the first four books. This book incorporates the author's insights and experiences from reading and traveling and may serve as a teaching reference for graduate and undergraduate students, to enhance the flexibility of statistical learning. Many people believe that economic statistics are only for quantitative analysis, but upon closer examination, the focus is on the "degree" of phenomena, that is, measurement.