The work is Kierkegaard's effort to replace what he believed had become an "amiable, sentimental paganism with authentic Christianity." Central to his existentialism is the fact that Jesus may be God as demonstrated through history and yet this is not what is necessary: faith is required. He describes the hiddenness of God and anything else is definitely paganism. For example, in his native Denmark he describes Christiandom as paganism. By contrast, God is hidden and mysterious and must be found and discovered but only through faith. A God that is clear and unmistakable and easily known is not God. Paganism is easily understood and is obviously false as a result.

"What, then, is the difference between an admirer and an imitator? An imitator is or strives to be what he admires, and an admirer keeps himself personally detached, consciously or unconsciously does not discover that what is admired involves a claim upon him, to be or at least to strive to be what is admired."

— Søren Kierkegaard, Practice in Christianity in the Essential Kierkegaard, p. 383-84

Practice in Christianity (also Training in Christianity) is a work by 19th century theologian Søren Kierkegaard. It was published on September 27, 1850 under the pseudonym Anti-Climacus, the author of The Sickness Unto Death. Kierkegaard considered it to be his "most perfect and truest book". In it, the theologian fully exposes his conception of the religious individual, the necessity of imitating Christ in order to be a true Christian and the possibility of offense when faced with the paradox of the incarnation. Practice is usually considered, along with For Self-Examination and Judge for Yourselves!, as an explicit critique of the established order of Christendom and the need for Christianity to be (re-)introduced into Christendom, since a good part of it consists in criticism of religious thinkers of his time.

The book discusses in detail one of Kierkegaard's most central notions such as "leap of faith" (or, to be more precise, "leap to faith") and "indirect communication". In other words, Kierkegaard emphasizes the idea that belief in God cannot and should not be rational in the sense that it cannot possibly be proved conclusively that God exists or that Christianity is true. In fact, Kierkegaard discounts the idea that a systematic Christian theology is possible. In this sense Kierkegaard (to the extent we could claim that he shared the views of the book's pseudonymous author) shared the anti-rationalist stance of Kant, the influential 18th-century philosopher.

Invocation
As long as there is a believer, this person, in order to have become that, must have been and as a believer must be just as contemporary with Christ’s presence as his contemporaries were. This contemporaneity is the condition of faith. P. 9

The Invitation
Come here to me, all you who labor and are burdened. This he says, and those who lived with him saw and see that there truly is not the slightest thing in his way of life that contradicts it. With the silent and veracious eloquence of action, his life expresses-even if he had never said these words-his life expresses: Come here to me, all you who labor and are burdened. He stands by his word or he himself is his word: he is what he says-in this sense, too, he is the Word. P. 14

If you are conscious of yourself as a sinner, he will not question you about it; he will not break the bruised reed even more, but will raise you up when you accept him. He will not identify you by contrast, by placing you apart from himself so that your sin becomes even more terrible. P. 20

“History,” says faith, “has nothing at all to do with Jesus Christ; with regard to him we have only sacred history (which is qualitatively different from history in general), which relates the story of abasement, also that he claimed to be God.” P. 30

The Halt
The sagacious and sensible person might say, “of course he does not invite me anyway; for he invites only those who labor and are burdened.” …. The philosopher might say, “it is madness for the single individual to want to be God. If this madness were possible, that an individual human being was God, then to be consistent one would have to worship this particular human being; a greater philosophical brutishness cannot be imagined.” The scoffer might say, “The contradiction is solely and only and exclusively the inventor’s: that a human being just like the rest of us, but not as well-dressed as the average person, therefore that a poorly dressed person who most likely belongs under the welfare department-that he is God.” P. 43, 48, 52

It is cunning of the inviter to say: I heal all sicknesses, and then when one comes says: I acknowledge only that there is one sickness-sin-of that and from that I heal all of those “who labor and are burdened,” all of those who labor to work themselves out of the power of sin, labor to resist evil, to overcome their weakness, but only manage to be burdened. Of this sickness he heals “all”; even if there were but one single person who turned to him on account of his sickness-he heals all. P. 61

That with which you are living simultaneously is actuality-for you. Thus, every human being is able to become contemporary only with the time in which he is living-and then with one more, with Christ’s life upon earth, for Christ’s life upon earth, the sacred history, stands alone by itself, outside history. P. 64

The Moral
And what does it all mean? It means that each individual in quiet inwardness before God is to humble himself under what it means in the strictest sense to be a Christian, is to confess honestly before God where he is so that he still might worthily accept the grace that is offered to every imperfect person-that is, to everyone. And then nothing further; then, as for the rest, let him do his work and rejoice in it, love his wife and rejoice in her, joyfully bring up his children, love his fellow beings, rejoice in life. P. 67

Blessed Is He Who Is Not Offended At Me
Fear yourself, fear what can kill the faith and in that way kills Jesus Christ for you-the offense. Fear and tremble, for faith is carried in a fragile earthen vessel, in the possibility of offense. P. 76

A Brief Summary Of The Contents Of This Exposition
The God-man is not the union of God and man-such terminology is a profound optical illusion. The God-man is the unity of God and an individual human being. P. 82

The Exposition
The generation wants to form the established order, to abolish God, in the fear of men to browbeat the single individual into a mousehole-but this God does not want, and he uses the very opposite tactic-he uses the single individual to prod the established order out of self-complacency. P. 89-90
The possibility of offense in relation to Christ qua God-man will continue until the end of time. If the possibility of this offense is taken away, it will mean that Christ, too, is taken away, that he is made into something different from what he is, the sign of offense and the object of faith. P. 93

One becomes a Christian only in the situation of contemporaneity with Christ, and in the situation of contemporaneity everyone will also become aware. P. 102

If I voluntarily give up everything, choose danger and difficulties, then it is impossible to avoid spiritual trial (which in turn is a specifically Christian category but of course has been abolished in Christendom), which comes with the responsibility (which in turn corresponds to the voluntary), when it is said: Why do you want to expose yourself to this and begin such a thing-after all, you could leave it alone. This is specific Christian suffering: it is a whole scale deeper than the ordinary human sufferings. P. 109

To commit a whole life to suffering, to sacrifice, is madness of the understanding. If I am to submit to a suffering, says the understanding, if I am to sacrifice something or in any way sacrifice myself, then I also want to be able to know what profit and advantage I can have from it-otherwise I would be a lunatic to do it. P. 116

The God-man (and, as said before, by that Christianity does not understand this fantastic speculation about the unity of God and man but an individual human being who is God) exists only for faith; but the possibility of offense is precisely the repulsion in which faith can come into existence-if one does not choose to be offended. P. 121

The Categories of Offense, That Is, of Essential Offense
Wherever it is the case that the teacher is an essential component, there is a reduplication; … that the teacher is the integral; … where there is reduplication communication is not direct. Reduplication in the teacher through his existing in what he teaches; all direct communication is impossible. P. 123

It was Christ’s free resolve from eternity to want to be incognito. He had superiority over himself in such a way that one seems lowlier than one is. P. 128-129

The possibility of offense is present at every moment, confirming at every moment the chasmic abyss between the single individual and the God-man over which faith and faith alone reaches P. 139

Eighteen hundred years have not contributed a jot to demonstrating the truth of Christianity. In proportion as the demonstration increased in power-fewer and fewer were convinced. P. 144

From On High He Will Call All To Himself
Lowliness, abasement, is the stumbling stone, the possibility of offense, and you are situated between his abasement, which lies behind, and his loftiness-that is precisely why he is said to draw to himself. The abasement belongs just as essentially to him as the loftiness. P. 153

Lord, increase my faith. The person who prayed this prayer was not an unbeliever but a believer. The person who prays this prayer aright must already feel himself drawn. Be aware of His presence. P. 156

Whether you or some person has adversities in life, whether things perhaps go downhill for him, or whether he perhaps loses his beloved: this is not called suffering like that of Jesus. Such sufferings are universally human, in which the pagans are tried as much as Christians. P. 173

This is the test: to become and continue to be a Christian, a suffering with which no other human suffering can be compared in pain and anguish. Yet neither Christianity nor Christ is cruel. No, Christ is himself leniency and love, is love and leniency itself; the cruelty comes from the Christian’s having to live in this world and having to express in the environment of this world what it is to b e a Christian-for Christ is not so lenient, that is, so weak, that he wants to take the Christian out of this world. P. 196

When the truth is the way, being the truth is a life-and this is indeed how Christ speaks of himself: I am the Truth, the Way and the Life-the illusion of the Church triumphant is that Christianity has been regarded as truth in the sense of results instead of it being truth in the sense of the way. P. 207

Only the Church militant is truth-the Church triumphant and established Christendom are an illusion. P. 219

Lord Jesus Christ, you did not come to the world to be served and thus not to be admired either, or in that sense worshiped. You yourself were the Way and the Life-and you have asked only for imitators. If we have dozed off into this infatuation, wake us up, rescue us from this error of wanting to admire or adoringly admire you instead of wanting to follow you and be like you. P. 233

When it comes to the moral, to want to admire instead of imitate is not an invention by bad people-no, it is the spineless invention by those who must be called the better but also weak people, whereby they seek to keep themselves detached. They are related to the admired one only though the imagination; to them he is like a theatrical play. P. 244

When the truth is the way there are “three ways to go wrong-to go the wrong way, to stumble on the way, to make a wrong turn away from the way”-we pray to you that you will draw the strayer back to yourself, will strengthen the stumbler on the way, will lead back to the way those who have gone astray. P. 262