The Problem with Agnosticism
The Agnostic position is that the existence of God is unknowable. This position assumes that the statement "God exists" is meaningful -- for it makes no sense to talk of not knowing the answer to a meaningless question.
If we look up 'exist' we find that it is basically defined as "to be". If we look up 'be' we find that it is basically defined as "to exist". So even on cursory examination we find that the definition of 'exist' is circular, and therefore meaningless. If you delve further into the philosophical meaning of 'exist' you quickly find that nobody can agree upon the word's meaning, and philosophers generally get themselves tied in knots trying to define it. Even when trying to be careful, the word is meaningless.
Since the word 'exist' is not well defined, the statement "God exists" is not well defined. The question of God's existence is meaningless.
The Agnostic position is that even though the question of God's existence is meaningless it is still a question worth consideration and that they do not know the answer.