Final answer:
Gabriel's New Realism acknowledges the existence of entities within fields of sense while drawing a line at the all-encompassing world-concept, in line with Kant's notion that existence is not a predicate that can be added to a concept.
Step-by-step explanation:
Markus Gabriel's New Realism posits that entities exist if they appear within a certain field of sense. This principle applies even to entities such as unicorns, which exist in the conceptual realm. However, Gabriel draws a distinction with the concept of an all-encompassing world, challenging the coherence of such a construct on grounds similar to the set-theoretic paradoxes, in line with global skepticism about the external world. Existence within Gabriel's framework is thus distinguished from Meinong's broader acceptance of entities, including inherently contradictory objects like a round square.
In contrast, Immanuel Kant's critique of Anselm's ontological argument underscores that existence is not a predicate that can be attributed to a concept to enhance its definition. This means conceptualizing an entity, such as God or unicorns, does not necessitate its literal existence; our conceptions do not equate to reality. Kant's assertion provides a philosophical backing for Gabriel's demarcation between entities within coherent fields of sense and the world-concept itself, which resists such neat incorporation into a field of sense due to its self-referential nature.