Final answer:
The question addresses the philosophical challenges of proving omniscience and the limitations in the concept of knowledge. Existence as a predicate, as critiqued by Immanuel Kant, and issues of subjective experience indicate that claims of omniscience may lack substantiation. Anselm's ontological argument also faces problems when connecting mental concepts with reality.
Step-by-step explanation:
The thought experiment you've outlined touches on important philosophical debates concerning the nature of knowledge, omniscience, and the limits of existence. Immanuel Kant critiqued the ontological argument for the existence of God, suggesting that existence is not a predicate that can simply be added to the definition of a being. Instead, asserting that something exists (like God or a perfect island) does not make it so in reality since existence outside the mind (extra-mentally) does not necessarily follow from mental conception (intra-mentally).
Anselm's ontological argument, on the other hand, claims that the concept of God is uniquely such that its existence is implied by its definition. However, this has been critiqued for conflating the mental concept of God with God's actual existence. In relation to the concept of an omniscient being, we run into issues when considering the possibility of subjective experiences or 'qualia'. If qualia are indeed subjective and unknowable to others, it introduces the possibility that there are aspects of reality that even an omniscient being could not truly comprehend or know.
Furthermore, the challenge of proving omniscience is inherently complex. Even assuming the existence of a higher power responsible for creating the universe, without the ability to objectively verify subjective experiences or to have complete confidence in the infallibility of memory and perception, the claim to omniscience remains unsubstantiated. These issues suggest that the concept of omniscience, as traditionally understood, encounters various philosophical challenges that question its coherence and viability.