12 Thus, We have reached one of the principal points in the Modernists' system, namely the origin and the nature of dogma. For they place the origin of dogma in those primitive and simple formulae, which, under a certain aspect, are necessary to faith; for revelation, to be truly such, requires the clear manifestation of God in the consciousness. But dogma itself they apparently hold, is contained in the secondary formulae. To ascertain the nature of dogma, we must first find the relation which exists between the religious formulas and the religious sentiment . This will be readily perceived by him who realises that these formulas have no other purpose than to furnish the believer with a means of giving an account of his faith to himself. These formulas therefore stand midway between the believer and his faith; in their relation to the faith, they are the inadequate expression of its object, and are usually called symbols ; in their relation to the believer, they are mere instruments .
Source: Pascendi Dominici Gregis (Vatican.va)