Let me provide a quote from (my nemesis), Richard Muller. He offers a definition of Martin Luther’s theologia crucis. Luther’s theology of the cross is at the very center of my mode as a Christian thinker. It has been with me ever since I studied it in Reformation theology class in seminary, back in 2002. I have a more constructive and detailed post on this (and many others), which you can read here. Consider this post as somewhat of an addendum to the post I just linked you to. Muller writes:

theologia crucis: theology of the cross; a term used by Luther and descriptive of his insight into the nature of revelation and therefore of theology as a whole. God has chosen to reveal himself, not as human describes him in its rational theology of glory (theologia gloriae, q.v.), but in the weakness and the scandal of the cross. True knowledge of God is, therefore, a knowledge of God that rests upon the hiddenness of God in his revelation, a knowledge that humbles worldly reason and wisdom. Like Luther’s distinction between God hidden and God revealed (Deus absconditus/Deus revelatus, q.v.), this concept of a theologia crucis militates against the marriage of theology and philosophy contemplated by the medieval scholastics.[1]

And the Apostle Paul’s theologia crucis,

For I determined not to know anything among you except Jesus Christ and Him crucified. –I Corinthians 2.2

This is the theological mode I slavishly prefer, as you know by now. I reject theologies that are grounded in speculative, discursive meanderings that are rooted in philosopher’s un-evangelized wits. As a Christian I am bond-slavishly committed to knowing God through God, as that is mediated through the vicarious humanity of Jesus Christ. There is no other Way, Truth, or Life. Luther would be appalled at the shape Reformation theology took, both in the Lutheran and Reformed traditions, post his death. I am appalled. Barth was appalled. Torrance was appalled.

[1] Richard A. Muller, Dictionary of Latin and Greek Theological Terms: Drawn Principally from Protestant Scholastics Theology (Grand Rapids, Michigan: Baker Book House, 1985), 300.