John Calvin famously begins his Institutes of the Christian Religion with a programmatic statement about the interrelation of knowledge of God and knowledge of oneself, in a sort of sanctification of the injunction of the Delphic Oracle:
Our wisdom, in so far as it ought to be deemed true and solid Wisdom, consists almost entirely of two parts: the knowledge of God and of ourselves. But as these are connected together by many ties, it is not easy to determine which of the two precedes and gives birth to the other. For, in the first place, no man can survey himself without forthwith turning his thoughts towards the God in whom he lives and moves; because it is perfectly obvious, that the endowments which we possess cannot possibly be from ourselves; nay, that our very being is nothing else than subsistence in God alone. In the second place, those blessings which unceasingly distil to us from heaven, are like streams conducting us to the fountain. Here, again, the infinitude of good which resides in God becomes more apparent from our poverty. In particular, the miserable ruin into which the revolt of the first man has plunged us, compels us to turn our eyes upwards; not only that while hungry and famishing we may thence ask what we want, but being aroused by fear may learn 38 humility. For as there exists in man something like a world of misery, and ever since we were stript of the divine attire our naked shame discloses an immense series of disgraceful properties every man, being stung by the consciousness of his own unhappiness, in this way necessarily obtains at least some knowledge of God. Thus, our feeling of ignorance, vanity, want, weakness, in short, depravity and corruption, reminds us (see Calvin on John 4:10), that in the Lord, and none but He, dwell the true light of wisdom, solid virtue, exuberant goodness. We are accordingly urged by our own evil things to consider the good things of God; and, indeed, we cannot aspire to Him in earnest until we have begun to be displeased with ourselves. For what man is not disposed to rest in himself? Who, in fact, does not thus rest, so long as he is unknown to himself; that is, so long as he is contented with his own endowments, and unconscious or unmindful of his misery? Every person, therefore, on coming to the knowledge of himself, is not only urged to seek God, but is also led as by the hand to find him. (Institutes 1.1.1)
The connection of these two kinds of knowledge was, however, much more widespread than Calvin, and applicable in a variety of contexts. Niels Hemmingsen makes a similar point when discussing the principles by which the true worship of God ought to be guided:
Hactenus de regula. Fundamentum cultus Dei sequitur, quod fixum et certum tenere oportet. Est autem hoc fundamentum duplex, nimirum cognitio Dei et cognitio nostri, de quibus quia abunde dictum est in prima Classe, hic brevius eadem attingemus. Cognitionem Dei consequimur per verbum et testimonium, quae coniuncta docent nos, quod Deus sit fons omnis virtutis, iusticiae, sapientiae et veritatis: quod Deo omnis gloria tribuenda sit: quod Deus ad iuvandum sit promtus sua natura: quod idem velit omnes ad se confugere in quovis periculo. Hanc Dei cognitionem esse fundamentum cultus Dei Esaias 19. docet his verbis: Cognoscent Aegyptij Dominum in die illo, et facient sacrificia et oblationem, vovebuntque vota Domino, et reddent.
Cognitio nostri ex trium rerum contemplatione petenda est, nimirum ex fine creationis, ex virium praesentium aestimatione, et ex facilitate lapsus in peccatum. Finis docet officium, quod est referre imaginem Dei in sincera pietate et iusticia vera. Vires ostendunt, quod officium debitum praestare minime valeamus. Lapsus frequentes nos monent fragilitatis nostrae et peccati. Unde admonemur omnem gloriandi materiam abijcere, ut qui fracti viribus nihil sine auxilio divino efficere boni possumus, Imo omni hora praecipites in nova peccata ferimur, nisi manu Dei conservemur. Sine hac nostri cognitione nec poenitentia, nec fides existere possunt: sine quibus nihil quantumvis speciosum Deo placere potest. Ubi hanc duplicem cognitionem Dei et nostri probe tenuerimus, fundamentum veri cultus Dei iactum est.
Thus far concerning the rule [regarding the worship of God]. The foundation of the worship of God follows, which one must hold as fixed and certain. This foundation is, moreover, twofold, namely, the knowledge of God and the knowledge of ourselves; because I treated these fulsomely in the first Division [of doctrines], I shall be brief in touching upon them here. We obtain the knowledge of God through the Word and the testimony, 1 which, joined together, teach us that God is the fount of all virtue, justice, wisdom, and truth; that all glory must be given to God; that God by his own nature is ready to help [us]; that he wishes all to flee to him in whatever danger [they find themselves]. Isaiah 19 teaches that this knowledge of God is the foundation of the worship of God in the following words: “The Egyptians will know the Lord in that day, and they will make sacrifices and an offering, and they will vow vows to the Lord, and will pay them.
The knowledge of ourselves should be sought from the contemplation of three things, namely, from the end of the creation, from the estimation of our present power, and from ease with which we fall into sin. The end teaches our duty, which is to bear the image of God in sincere piety and true justice. Our powers demonstrate that we are not are not able to perform the duty that is owed. Our frequent falls remind us of our weakness and sin. From this we are admonished to cast away all matter for boasting, since we, broken in our power, can bring about nothing good without divine aid–nay, rather, we are carried every hour headlong into new sins–unless we should be preserved by the hand of God. Without this knowledge of ourselves, there can be neither repentance nor faith, without which nothing, howsoever splendid, can please God. When we honestly possess this twofold knowledge of God and of ourselves, the foundation of the true worship of God has been laid. 2 (Enchiridion Theologicum, pp. 172-3)
A couple of observations: Hemmingsen makes the important point that we cannot truly worship God without knowing him; and in order for us to know him God must reveal himself, such that the Word and the testimony is the foundation for the knowledge of God, and thus of true worship. These teach us the goodness and supremacy of God as he actually is.
The knowledge of ourselves, on the other hand, teaches us what we should be and are not. It teaches us of the loftiness of our created state–the remarkable power and ability with which we were first endowed–and the way in which we have shattered it through sin. In this way, self-knowledge brings about humility (and thus his point is not unrelated to what was probably the purport of the Delphic injunction “Know yourself,” a knowledge which should render us humble). It is only the action of God that preserves us, and our acknowledgement of this fact should lead to repentance and faith in him, which is requisite for our doing anything that pleases him.
When we have properly gained an estimation of God’s greatness and our lowliness, then–and only then–can we begin to worship him truly.