John Calvin on Having Our Own Views of God

"We must hold, that whosoever adulterates pure religion (and this must be the case with all who cling to their own views), make a departure from the one God.  No doubt they will allege that they have a different intention; but it is of little consequence what they intend or persuade themselves to believe, since the Holy Spirit pronounces all to be apostates, who, in the blindness of their minds, substitute demons in the place of God.  For this reason Paul declares that the Ephesians were 'without God' (Eph. 2:12), until they had learned from the gospel what it is to worship the true God" (John Calvin, Institutes of Christian Religion).