Furnished with reason that has a heart

In Luther's brilliant exposition of the First Commandment in his Large Catechism he says something rather strange:

it is the trust and faith of the heart alone that make both God and an idol.

Oswald Bayer, in his explanation of Luther's theology of the human being explains where that sort of thinking is coming from:

The human being is animal rationale, habens cor fingens - a being furnished with reason that has a heart, which imagines, makes pictures, invents...There are thus two basic powers that drive the human being - his rational consciousness and his utopian consciousness. The one defines the intellectual interaction with the world of human beings and is primarily oriented toward the present; the other is located in the realm of the imagination, which focuses primarily on the past and the future - interpreting the past and projecting into the future....The power of imagination fabricates images - sketches of goals for life, of happiness, as well as images of fears about disaster. They are all rational remembrances, diagnoses, prognoses, guided by images that the human heart has imagined and produced, by pictures of fear and hope, which once again are grounded in certain experiences.

Luther's definiton of the human being as an animal rationale, habens cor fingens has its theological validity within creation, but is to be understood first of alll...as a theological description of sin.... In an exactly parallel way, Calvin says: "the fantasy of the human being is a factory that works ceaselessly to make idols."

This is correct if the circumstances of the sinful situation are at are at issue. But at the same time, that which identifies what is appropriate to the creation in this formula still remains: even in faith I am cor fingens, in that I praise God by letting God by God, in that I, when I - in spiritual, spirit motivated (Col 3:16) creativity - accord to him what is appropriate to him. The cor fingens is at work even in a poetic song of praise, but in the sense that it offers thanks. Thus Luther's famous phrase fides creatrix divinitatis [faith is the creator of divinity] is to be understood as follows: the faith is the creator of the deity, to be sure, non in persona sua, sed in nobis - not in and of itself, but in us. We make God to be God, that we give him what is due to him; we let God be God.

(pp.174-175, Martin Luther's Theology: A Contemporary Interpretation)

Can't say I understand it deeply, or that I know what to make of it. But its interesting.