Husserl's "Logical Investigations" is one of the most detailed books ever written on the phenomenology of consciousness. The two volumes published in 1900 ("Prolegomena") and 1901 ("Logical Investigations") not only contribute to the topics of meaning, concept, judgment, knowledge, and truth, which were widely discussed in the logic books of the time, but they also extend these analyses to acts of consciousness, such as perceptions, imaginations, feelings, and intentionality in general. Continuously referencing insights from earlier chapters, they ultimately connect to form a comprehensive overall picture of the structure of mental experiences. In doing so, they provide important contributions to contemporary debates in epistemology and the philosophy of mind. The phenomenological method is increasingly proving to be an indispensable source in philosophy.