The book "Active Syntheses: From the Lecture 'Transcendental Logic' 1920/21" offers a comprehensive analysis of the final parts of Edmund Husserl's lecture delivered in the winter semester of 1920/21. This supplementary volume to Husserliana Volume XI provides the original version of the lecture in its entirety and sheds light on the development of Husserl's philosophy, particularly the transition to genetic phenomenology. This work is of central importance as it analyzes the transcendental-logical foundations of passive synthesis, thus providing deep insights into Husserl's thinking. The author, Roland Breeur, has carefully prepared the content to clarify the relevance and context of the lecture. This work is not only of interest to students of philosophy but also to anyone who wishes to engage with the development of the phenomenological method.