My listeners! If you are willing, let us recall the direction that our talk has taken. If a man should will one thing, then he must will the Good, for in this way alone was it possible for him to will a single thing. If, however, it is to be genuine, he must will the Good in truth. According to whether he is an active one or a sufferer he must be willing either to do all for the Good, or he must be willing to suffer all for the Good. He must be willing either to do all for the Good,k or to be and to remain committed to the Good. But cleverness may be misused internally, to seek evasions; and misused externally in deception. The good man, on the contrary, uses cleverness to cut off all evasions and thereby to launch out and to remain constant – in the commitment. He also uses cleverness to prevent such external deception. He must be willing to suffer all for the Good, or to be and to remain committed to the Good. And the talk went on to describe the true sufferer’s condition, because by looking at sufferings one may really learn what the highest is. Once again in regard to suffering, cleverness may be misused internally to seek ways of escape, but the Good man makes use of just this very cleverness against ways of escape, in order that he may be and remain committed to the Good, by being willing to suffer all, by accepting the enforced necessity of suffering.
But purity of heart is to will one thing. It is this thesis that has been the object of the talk which we have linked to the apostolic words: “Draw nigh to God and he will draw nigh to you, cleanse your hands, ye sinners, and purify your hearts, ye double-minded!” For commitment to the Good is a whole-souled decision, and a man cannot by the craft and the flattery of his tongue lay hold of God while his heart is far away. No, for since God is spirit and truth, a man can only draw near to Him by sincerity, by willing to be holy, as He is holy: by purity of heart. Purity of heart: it is a figure of speech that compares the heart to the sea, and why just to this? Simply for the reason that the depth of the sea determines its transparency. Since the sea is pure only when it is deep, and is transparent only when it is pure, as soon as it is impure it is no longer deep but only surface water, and as soon as it is only surface water it is not transparent. When, on the contrary, it is deeply and transparently pure, then it is all of one consistency, no matter how long one looks at it; then its purity is this constancy in depth and transparency. On this account we compare the heart with the sea, because the purity of the sea lies in its constancy of depth and transparency. No storm may perturb it; no sudden gust of wind may stir its surface, no drowsy fog may sprawl out over it; no doubtful movement may stir within it; no swift-moving cloud may darken it: rather it must lie calm, transparent to its depths. And today if you should see it so, you would be drawn upwards by contemplating the purity of the sea. If you saw it every day, then you would declare that it is forever pure – like the heart of that man who wills but one thing. As the sea, when it lies calm and deeply transparent, yearns for heaven, so may the pure heart, when it is calm and deeply transparent, yearn for the Good. As the sea is made pure by yearning for heaven alone; so may the heart become pure by yearning only for the Good. As the sea mirrors the elevation of heaven in its pure depths, so may the heart when it is calm and deeply transparent mirror the divine elevation of the Good in its pure depths. If the least thing comes in between, between the heavens and the sea, between the heart and the Good, then it would be sheer impatience to covet the reflection. For if the sea is impure it cannot give a pure reflection of the heavens.
-Soren Kierkegaard, in ch. 11