Sursum cor => Gratias agere

The true relation of the eucharist as [a] healing purgatio is [most] profound. Remember that the Eucharist represents the sacrifice of the heart of the whole Church. Because of that, with profound reason the saying "Sursum cor" is placed at the very beginning. In it the internal content of this sacrament is really expressed: the "being in God" of our heart, that is, of the homo interior. Note that that "being with God" is expressed with the word "above" (sursum). With that, in the first place, is said that everyone who rightly does Christian worship has already surpassed the ladder and is in the above in which he does not any longer need any mediation from the devils, because he has long since left the devils behind him. But it is furthermore also said that Augustine has taken the spatial determination of our relationship with God seriously. He who is in God is necessarily also in the spatial supra-celestial; the true city of God in contrast to the city of the gods is "above", is the civitas superna. Consequently, it is formed by the "gods", i.e. by the angels, and it has, furthermore, so to speak, a colony on earth. This does not change the fact that the city as such is in heaven, in the intelligible world above, and that those who are above are thus not at home, but rather "in a foreign land, far from the Lord". Our homecoming means, according to this, the entering into the company of the angels; the goal proposed to man is to become an angel. But this goal has not yet been achieved, and that in a general way: neither by the living nor by the dead Christian faithful. What is more, the introduction of the human race, coming from the cosmic space to which it is subject by the actual characteristics of its nature, to a cosmic environment for which it is not yet prepared, presupposes a cosmic transformation or a transformation of human nature: the resurrection of the flesh and the new creation. For now this entire community of the elect keeps itself on the foreign land of this hour. Admittedly, in a certain sense it is already above, just like the sursum cor expresses it in the sacrificial celebration. It is above according to faith and hope.

In this way faith is changed into a first resurrection, to the degree that it institutes an anticipated form of our future being. And, according to this, the communion of the baptized, the Church, is a prefigure of the reign of God, to the degree in which it is the unity of the resurrected in this way and, with that, a prefigure of their "being one" with the city above. The opposition between faith and intellectus is represented at this level as a sort of eschatological-cosmic difference, given that the faith represents the provisional form of contact with God, of dwelling in the diving closeness, with the intellectus expresses the true and manifest encountering in the ontological space of God. And we would still add this: the eschatological determination has validity with the same force for the civitas Dei as for the civitas terrena. The fact that the devils, that is, the fallen angels, continue to dwell in the area of the air, is only comprehensible conscious of the provisional nature of the present state of the world. They are already damned beforehand. In the end of days they will be sent to the abyss, which is their genuine place.

If we contemplate these explanations now in perspective, we see the following: the purification of Christians is not an intellectual process, but rather it is realized by the sacramentum and by the res offered by it, it happens like grace from above, which draws man. The highest ascent of man takes place now in no other way, except by the divine descent. The fault of the philosophers consists in not wanting to submit to this order. For Augustine the holding of the salvific exclusivity of the Church in face of the philosophers would mean a difficult problem. For clearly these found themselves already in some way at the goal, to the degree that they had knowledge of the triune God. And the incarnation of Christ and all the visible salvific elements were only a means for attaining the goal. Could he who arrived at the goal without the means be reproached? Him who had his heart above, even without the external signs of the Church? He could! For, even though the philosophers were not missing the raising of the heart, the sursum cor. the were missing, however, the gratias agere: the correct response with God. "Although they knew God, they did not glorify Him as God or give thanks." (Rom 1:21)

Joseph Ratzinger, Obras Completas I (1951 thesis on Augustine), Madrid: BAC, 2014, pp. 256-259

...The connection between the visible worship of the Church and the worship of the love of the heart has its corresponding expression in the "sursum cor",* repeatedly cited, which places the altar of that sacrifice in the heart of the Christian, on the one hand, and it makes us become always aware at the same time, on the other hand, of the bond between the love of the heart with the visible union of love of the Eucharistic community.

*..."Cum ad illum sursum est, eius est altare cor nostrum"; cf. En in Ps 37,10 (PL 36,401); C Parm III 3,19 (PL 43,97); Serm Denis VI,2 (ed. Morin, 31); Guelf  XX (ed. Morin, 504-506) (cf. Balthasar, Das Antlitz deer Kirche, texto 119). Through this term Augustine has expressed a central purpose of his theology and has endowed it with a rich interpretation, taken from the nucleus of his thought; cf. especially Civ XIV 13,1 (421): "Est igitur aliquid humilitatis miro modo quod sursum faciat cor et est aliquid elationis, quod deorsum faciat cor. Hoc quidem quasi contrarium videtur, ut elatio sit deorsum et humilitas sursum". The relationship between humiltas and caritas, which is evidently very close, would still need an investigation dedicated to it.

p. 240, footnote 75