Specific Content - Our knowledge and understanding of our faith comes from three sources:
Where is the space for open-ended content?
Religious tradition and practice
From the Catechism of the Catholic Church Part One, Section 1.2
32 The world: starting from movement, becoming, contingency, and the world's order and beauty, one can come to a knowledge of God as the origin and the end of the universe.
As St. Paul says of the Gentiles: For what can be known about God is plain to them, because God has shown it to them. Ever since the creation of the world his invisible nature, namely, his eternal power and deity, has been clearly perceived in the things that have been made.7
And St. Augustine issues this challenge: Question the beauty of the earth, question the beauty of the sea, question the beauty of the air distending and diffusing itself, question the beauty of the sky. . . question all these realities. All respond: "See, we are beautiful." Their beauty is a profession [confessio]. These beauties are subject to change. Who made them if not the Beautiful One [Pulcher] who is not subject to change?833 The human person: with his openness to truth and beauty, his sense of moral goodness, his freedom and the voice of his conscience, with his longings for the infinite and for happiness, man questions himself about God's existence. In all this he discerns signs of his spiritual soul. the soul, the "seed of eternity we bear in ourselves, irreducible to the merely material",9 can have its origin only in God.
So we can know about God through direct interaction with Creation and through our own human nature which contains God's stamp.
There IS a place for open-ended content in RE because EVERYTHING is RE.