 Thus, when Hegel in the second edition of his Science of Logic (1831) nevertheless claims that in the end “[e]very philosophy is essentially idealism or at least has it as its principle” (GW 21, 142), he must mean by idealism something other than traditional idealism and certainly something other than Kant’s indeterminate ontological realism. Rather, he must mean by idealism a philosophical outlook that is immune against the charge of grounding a philosophical system in a conception of reality that is committed to the acceptance of any irreconcilable oppositions. Now, for Hegel the most fundamental opposition both from a systematic and a historical perspective is the opposition between thinking and being, or rather, in the preferred terms, between subject and object. Looked at from a systematic perspective, this opposition is fundamental because of its apparent unavoidability, already at a descriptive level, when it comes to an assessment of the ultimate characteristics of reality: after all, we want to be able to hold fast to the distinction between what is only (in) our (subjective) thought and what is (objectively) the case. Considered from a historical point of view it shows that—at least within the tradition of occidental philosophy—the opposition between thinking and being lies at the bottom of the most influential attempts (with very few exceptions like Parmenides and possibly Spinoza) to give a philosophical account of the essence of reality and its multifarious ways of appearing to us. The traditional conviction of the fundamental and irreconcilable opposition between thinking and being finds expression in many different ways. These ways include the belief that there is being that is totally independent of or without any relation to thinking, or the conviction that thinking is somehow external to being in that being is just the self-standing provider of material on which a by itself contentless (inhaltslos) thinking imposes a certain conceptual form, or the assumption that even if there were no thinking there would be being and vice versa. However, according to Hegel it can be demonstrated that to think of thinking and being as fundamentally opposed in any of these ways leads to inconsistencies resulting in contradictions, antinomies and other bewildering deficiencies. Hence an idealistic philosophical system that is to overcome these deficiencies has to get rid of the underlying fundamental opposition and to show that thinking and being are not opposed but ultimately the same. This claim as to the sameness or the identity of thinking and being (subject and object) is the cornerstone of Hegel’s metaphysical credo and together with some other assumptions leads relatively smoothly to a version of ontological monism as the only convincing shape of an idealistic system.