This article attempts to answer the question as to why one should study Cohen. The author’s first and preliminary answer is that the study of Hermann Cohen’s thought is relevant to contemporary philosophy due to at least five reasons: (1) Cohen’s improvement of critical idealism of subject through replacing it with the idealism of ideas; (2) the exposition of thought as the ethics of law; (3) the development of the notion of anticipation as the principle of time, history, and interpretation; (4) the exposition of critical idealism as a form of idealism that is not violent, totalitarian or reductive, but rather is an idealism aimed at alterity and the other; (5) the role of history and especially the history of Judaism in constructing a religion of reason and the developing the concept of Judaism. According to Cohen, thinking is the thinking of first elements. However, he understands the first elements not only as the beginning of any thinking process, but also as the first principle of critical thinking, whereas the ‘first principles’ of critical thinking are the act of questioning. Cohen believes that thinking is generated from itself. Thinking sets itself as the goal and objective, which emphasises the self-expanding nature of thinking, the original self-generation. Initially, thinking is one of the meanings of the term ‘pure’, which suggests that thinking in itself — rather than external influences — is an impetus for the movement,. It is concluded that, having overcome the dualism of reception and spontaneity, critical idealism received a positive impulse. They are consistent with each other, because the idea — understood as a hypothesis — forms the basis for (scientific) knowledge. Therefore, critical idealism can be defined as the idealism of ideas as opposed to the idealism of the subject. According to Cohen, thinking is shaped in the course of making judgments. Judgment determines the ratio between two different concepts; therefore, Cohen defines judgment as an act of ‘separation’ and ‘association’. This means that the judgment is an act of generation through the variable directions of separation and association. Thus, the Marburg philosopher defines discursive thinking as a correlation between separation and association. Therefore, discursive thinking can be defined as the penetration and preservation of the direction variables of separation and association activities. This means that the preservation of direction variables is a distinctive feature representing a scheme of thinking and, therefore, a system of philosophy. Schemes of thinking are not determined by synthesis or removal, but rather by preservation. In conclusion, it is possible to state that, in Cohen’s critical idealism, this belongs to the basic structure of the pure activity, which generates thought, and that thought is a sign of otherness and the other.