Not a single agnostic is prepared in the end to restrict himself or herself to saying that the matter [whether there is a God] is unclear (non liquet). Spencer, for example, keeps saying that we do not know the Absolute; at the same time he has an idea of it, demonstrates its existence, and assigns an array of properties to it. He asserts that it is not a negative but a positive concept; that it is the cause of everything; that is is a power mostly analogous to our will, infinite, eternal, omnipresent (etc.). This certainly is no longer agnosticism, but a very specific kind of knowledge and a rather well-defined God-concept. Agnosticism, inherently untenable and afraid of atheism, serves in the end to justify a pantheistic God-concept.
Reformed Dogmatics Vol. 2: God and Creation (Grand Rapids, Michigan; Baker Academic; 2004) p. 51-52.