The question here is the authority of the God and the ability of God to reveal Himself, His will, and His knowledge to humanity. It is common for and Agnostic who uses the tag, "Christian," to use circular reasoning.  They are seeking to prove that God doesn't communicate.  It is circular reasoning when they, in any way, give as evidence the very thing that they are trying to prove.

Agnosticism is the notion that no one can know anything about God.Agnostics not only believe that they know nothing about God, but they also feel that no one else knows anything about God. However, everyone knows that God is. Romans1:19 Because that which may be known of God is manifest in them; for God has showed it to them. 1:20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: You see? You know because God has showed it to you and to all of us.

Agnostic Christianity is very common among the liberal Christians, but it is not uncommon among Christians who consider themselves conservative. There are many who think that they are far better off depending on the god of raw human reasoning (the reasoning of the human mind without the Intelligence of the Creator flowing through the human mind) rather than the God of the Bible. They try to understand the Bible by the power of raw human reasoning (the reasoning of the human mind without the Intelligence of the Creator flowing through the human mind) even though the Bible says that the natural man cannot receive the things of the Spirit of God. They deny such things as prophecy, the word of wisdom, or the word of knowledge. They prefer, instead, a rationalized explanation of Scripture.