19 世紀基督教思想家齊克果以「存在主義之父」聞名，他在哲學方面與龐大的黑格爾思想體系交鋒，而在神學方面則與巨大的國家教會體系作戰。
他是一位信仰騎士，主張信仰不是理解與否的問題，更不是利害算計的問題，而是一種投向未知的跳躍，必得先能捨棄理性思考而懸擱倫理道德，而後才能進入信仰。
國家教會體制把人人都視為基督徒，以致再也無法清楚究竟誰是基督徒，結果是新約裡的基督教消失了。齊克果因而宣稱，只有個別的基督徒才是真實存在的基督徒。回歸之道在於閱讀聖經而看見自己，而當時的神學學術研究卻以客觀的學術取代了主觀的信仰，擔任牧師職分者卻又被體制馴化而不再有勇氣說出真話。
路德也是一位信仰騎士，然而齊克果所批判的國家教會卻是路德宗教改革所建立的教會。齊克果一方面肯定路德重新發現「因信稱義」的真理，另一方面卻批判路德的信仰理想並未真正落實，因為「因信稱義」的教義帶來忽略好行為的副作用，以致損毀了對上帝的「信」，宗教改革應當是一種繼續進行中的運動而非僵化的傳統典範。
信心騎士的首要特徵就是效法基督的實踐行動，由於效法基督意味著與世界衝突，基督教界的問題癥結，就在於不再效法基督。一百年後神學家潘霍華對廉價恩典的批判以及對重價恩典的呼籲，都回應了齊克果的心聲，二人同樣在壯年去世，也都是不斷地作那不可能之夢的信仰騎士。

The Christian thinker Kierkegaard of 19th is well known as “the father of
existentialism”. He has criticized the huge Hegelian system in the field of
philosophy, and fought with the giant state church system in the field of theology.
He is a knight of faith, who contends that faith is prior to understanding and calculating. As a knight of faith who leaps into the unknown, it is necessary to forsake reasoning and leave aside ethics in order to get involved into faith.
The system of state church has included everyone as Christian, so that it is hardly possible to discern who a real Christian is. The result is that the Christianity in the New Testament disappears. In contrast with this, Kierkegaard claims that it is possible only for an individual to be a real Christian. The solution lies in reading Bible in order to see oneself clearly. But the theological research has replaced the subjective faith with the objective academic, and those who hold the positions of pastors have been tamed and lacked courage to tell the truth.
Luther is also a knight of faith, but the state church criticized by Kierkegaard has been founded by him. On the one hand, Kierkegaard approves the re-discovery of the doctrine of Justification by Faith. On the other hand, he criticizes that the ideal of Luther has not come true. On account of justification there is a side-effect of neglecting good works which spoils faith. Reformation should be a moving on reform instead of a rigid traditional model.
The primary character of a knight of faith is the action of imitating Christ.
This means conflict with this world that is refused by Christendom. One hundred years later, the critique of cheap grace and the appeal of costly grace of Bonhöffer have well responded to the thought of Kierkegaard. The two die at the age of the prime of life and are therefore knights of faith who dream the impossible dream unceasingly.