Auguste DeMorgan's First Concepts of Logic (Preparation for Geometry) is an essential textbook for those who wish to understand the basic principles of logic before delving into geometry. DeMorgan reveals key aspects of thinking and develops skills in analysis and reasoning. The author offers readers systematic and accessible information on logical operations, syllogistics, categorical sources, analysis and synthesis of statements. This book is indispensable for anyone interested in the development of logical thinking and the construction of evidence mechanisms in their cognitive process.