This dissertation’s guiding question is: What was the impact of Martin Heidegger’s early philosophy on Dietrich Bonhoeffer’s theology? I argue that Heidegger’s analysis of Dasein, his technical term for human existence, provides Bonhoeffer with important conceptual tools for developing his Christology, from which the rest of his theology follows. Part of recognizing Heidegger’s importance to Bonhoeffer involves understanding the latter’s critiques of previous notable philosophers such as Kant, Hegel, Husserl, and Scheler. As Bonhoeffer evaluates these philosophers, they lead to theologically unacceptable positions. Heidegger, in contrast, has come to a theologically profitable understanding of human existence and epistemology. Though there are theologically useful elements in Heidegger’s philosophy, there are elements that require significant alteration, and even rejection. Heidegger recognizes that epistemology must be based on actual human existence, and he can account for the historical continuity of human existence; however, because of Heidegger’s anthropocentric philosophy, he cannot account for God’s transcendence necessary for proper theology. Bonhoeffer then applies the conceptual tools he has appropriated from Heidegger to revelation, Christology, and the church. This eliminates the anthropocentrism that made transcendence impossible, while maintaining the benefits of Heidegger’s philosophy in order to account for Christian existence. Understanding Bonhoeffer’s appropriation of Heidegger is additionally important for understanding Heidegger’s potential relation to theology. This dissertation concludes by placing Bonhoeffer in the context of other theological appropriations of Heidegger. In light of this context and Heidegger’s own understanding of philosophy’s relation to theology, I argue that Bonhoeffer represents one, viable theological use of Heidegger.

Segundo Tomás de Aquino, a forma é o que instancia a substância em determinada natureza; sem ela, a substância não seria o que é. Saliente-se que definir o que é (quid est) algo não é o mesmo que afirmar que ele é, pois, neste caso, o que é afirmado é sua existência, não sua natureza. Isso indica que a existência não é posta pela forma da substância, mas por algo outro, que, em sua Exposição aos Ebdomadibus de Boécio, Tomás chama de ato de ser (actus essendi). Imiscuído na substância que é seu sujeito , o ato de ser concede-lhe existência, tornando-a um ente, o qual possui um vínculo com o próprio ser (ipsum esse), que é deus. O aquinatense chama esse vínculo de participação, donde o ente participa do ser tal como o efeito de sua causa. O problema é instaurado quando se passa do plano ontológico ao gnosiológico, isto é, quando o intelecto busca inteligir a participação do ente no ser. Nessa intelecção, a limitação do intelecto humano se evidencia: a participação do ente no ser é entendida não como tal, mas como a do concreto no abstrato. O ente é significado em concreto, pois nele o ato de ser se encontra concretizado; a dificuldade, contudo, apresenta-se quando o intelecto tenta abstrair o ato de ser do ente: nessa abstração, o ato de ser não é inteligido enquanto tal, mas enquanto abstrato. Diante disso, torna-se inevitável levantar as seguintes questões: qual o modo de abstração que tenta obter o ato de ser do ente? Por que o intelecto não é capaz de inteligir o ser enquanto ser, mas apenas enquanto abstrato? O ato de ser, inconcebível pelo intelecto humano, é de fato superior à forma substancial? A participação do concreto no abstrato corresponde à do ente no ser? São estas as principais questões que, neste estudo, buscaremos responder. / According to Thomas of Aquinas, form is that which instantiates substance in a determinate nature; without it, substance would not be what it is. It should be emphasized that defining what something is (its quid est) is not not the same as to assert that it is, for in this case what is asserted is its existence, not its nature. That indicates that existence is not given by the form of the substance, but by something else, which in his Exposition to the Boethius\'s Ebdomadibus, Thomas calls act of being (actus essendi). Mingling in the substance its subject , the act of being gives it its existence, turning it into an entity, which is vinculated to being itself (ipsum esse), or God. The Aquinate calls this nexus participation, whence the entity participates in being as the effect of its cause. The problem is set when one traverses the ontological level to the gnoseological, that is, when the intellect tries to grasp the participation of the entity in being. In this intellection, the limits of the human intellect become clear: the participation of entity in being is understood not as such, but as the concrete in relation to the abstract. The entity is signified in concrete, for in it the act of being is found concretized; the difficulty, however, reveals itself when the intellect tries to abstract the act of being from the entity: in this abstraction, the act of being is not grasped as such, but as abstract. Thus it becomes inevitable to formulate the following questions: which is the mode of abstraction which tries to obtain the act of being of the entity? Why is the intellect not able to grasp being as being, but only as abstract? Is the act of being, inconceivable to the human intellect, in fact superior to the substantial form? And does participation of the concrete in the abstract correspond to that of the entity in being? These are the main questions that this study aims to answer.

Segundo Tomás de Aquino, a forma é o que instancia a substância em determinada natureza; sem ela, a substância não seria o que é. Saliente-se que definir o que é (quid est) algo não é o mesmo que afirmar que ele é, pois, neste caso, o que é afirmado é sua existência, não sua natureza. Isso indica que a existência não é posta pela forma da substância, mas por algo outro, que, em sua Exposição aos Ebdomadibus de Boécio, Tomás chama de ato de ser (actus essendi). Imiscuído na substância que é seu sujeito , o ato de ser concede-lhe existência, tornando-a um ente, o qual possui um vínculo com o próprio ser (ipsum esse), que é deus. O aquinatense chama esse vínculo de participação, donde o ente participa do ser tal como o efeito de sua causa. O problema é instaurado quando se passa do plano ontológico ao gnosiológico, isto é, quando o intelecto busca inteligir a participação do ente no ser. Nessa intelecção, a limitação do intelecto humano se evidencia: a participação do ente no ser é entendida não como tal, mas como a do concreto no abstrato. O ente é significado em concreto, pois nele o ato de ser se encontra concretizado; a dificuldade, contudo, apresenta-se quando o intelecto tenta abstrair o ato de ser do ente: nessa abstração, o ato de ser não é inteligido enquanto tal, mas enquanto abstrato. Diante disso, torna-se inevitável levantar as seguintes questões: qual o modo de abstração que tenta obter o ato de ser do ente? Por que o intelecto não é capaz de inteligir o ser enquanto ser, mas apenas enquanto abstrato? O ato de ser, inconcebível pelo intelecto humano, é de fato superior à forma substancial? A participação do concreto no abstrato corresponde à do ente no ser? São estas as principais questões que, neste estudo, buscaremos responder. / According to Thomas of Aquinas, form is that which instantiates substance in a determinate nature; without it, substance would not be what it is. It should be emphasized that defining what something is (its quid est) is not not the same as to assert that it is, for in this case what is asserted is its existence, not its nature. That indicates that existence is not given by the form of the substance, but by something else, which in his Exposition to the Boethius\'s Ebdomadibus, Thomas calls act of being (actus essendi). Mingling in the substance its subject , the act of being gives it its existence, turning it into an entity, which is vinculated to being itself (ipsum esse), or God. The Aquinate calls this nexus participation, whence the entity participates in being as the effect of its cause. The problem is set when one traverses the ontological level to the gnoseological, that is, when the intellect tries to grasp the participation of the entity in being. In this intellection, the limits of the human intellect become clear: the participation of entity in being is understood not as such, but as the concrete in relation to the abstract. The entity is signified in concrete, for in it the act of being is found concretized; the difficulty, however, reveals itself when the intellect tries to abstract the act of being from the entity: in this abstraction, the act of being is not grasped as such, but as abstract. Thus it becomes inevitable to formulate the following questions: which is the mode of abstraction which tries to obtain the act of being of the entity? Why is the intellect not able to grasp being as being, but only as abstract? Is the act of being, inconceivable to the human intellect, in fact superior to the substantial form? And does participation of the concrete in the abstract correspond to that of the entity in being? These are the main questions that this study aims to answer.

Nous entendons, dans ce mémoire, préciser le sens d'actus essendi par l’analyse de l’emploi du terme par Thomas d’Aquin. Bien que la notion d’acte d’être soit sousjacente à nombre de développements philosophiques et théologiques de l’Aquinate, elle n’est considérée pour elle-même dans aucun texte du corpus thomasien. En exposant le cadre théorique des onze unités textuelles dans lesquelles on retrouve nommément l’expression, nous explicitons les distinctions qu’opère Thomas entre l’acte d’être et les notions ontologiques corrélatives (étant, quiddité, être du jugement prédicatif et être commun). Si « actus essendi » désigne en premier lieu un principe constitutif de l’étant, il peut encore désigner le terme abstrait correspondant à cette perfection de l’étant. L’acte d’être est ainsi ce par quoi l’étant est étant; il est cependant, au plan ontologique, propre à chaque étant singulier tandis que, au plan conceptuel, le même terme exprime ce qui est commun à tous les étants. Une traduction des extraits du Scriptum super Sententiis, des Quæstiones de quolibet, de la Summa Theologiæ, des Quæstiones disputatæ De potentia, de l’Expositio libri De hebdomadibus et de la Expositio libri Metaphysicæ a été produite pour les fins de cette étude. / In this paper, we intend to precise the meaning of actus essendi by analyzing how Thomas Aquinas uses this term. If the notion of the act of being underlies a number of Aquinas’ philosophical and theological developments, it is not treated in itself in any of his writings. By exposing the theoretical framework of the eleven textual units in which the expression namely appears, we explicate how he distinguishes between the act of being and the correlative ontological notions (the being, the essence, the predicamental judgment being and common being). If « actus essendi » first designates a constitutive principle of being, it can also designate the corresponding abstract term of this perfection of being. The act of being is that by which being is being; however, it belongs, at the ontological level, to each particular being whereas at the conceptual level, the same term expresses that which is common to all beings. Extracts of the following texts have been translated in French for this purpose: Scriptum super Sententiis, Quæstiones de quolibet, Summa Theologiæ, Quæstiones disputatæ De potentia, Expositio libri De hebdomadibus and the Sententia libri Metaphysicæ.

Nous entendons, dans ce mémoire, préciser le sens d'actus essendi par l’analyse de l’emploi du terme par Thomas d’Aquin. Bien que la notion d’acte d’être soit sousjacente à nombre de développements philosophiques et théologiques de l’Aquinate, elle n’est considérée pour elle-même dans aucun texte du corpus thomasien. En exposant le cadre théorique des onze unités textuelles dans lesquelles on retrouve nommément l’expression, nous explicitons les distinctions qu’opère Thomas entre l’acte d’être et les notions ontologiques corrélatives (étant, quiddité, être du jugement prédicatif et être commun). Si « actus essendi » désigne en premier lieu un principe constitutif de l’étant, il peut encore désigner le terme abstrait correspondant à cette perfection de l’étant. L’acte d’être est ainsi ce par quoi l’étant est étant; il est cependant, au plan ontologique, propre à chaque étant singulier tandis que, au plan conceptuel, le même terme exprime ce qui est commun à tous les étants. Une traduction des extraits du Scriptum super Sententiis, des Quæstiones de quolibet, de la Summa Theologiæ, des Quæstiones disputatæ De potentia, de l’Expositio libri De hebdomadibus et de la Expositio libri Metaphysicæ a été produite pour les fins de cette étude. / In this paper, we intend to precise the meaning of actus essendi by analyzing how Thomas Aquinas uses this term. If the notion of the act of being underlies a number of Aquinas’ philosophical and theological developments, it is not treated in itself in any of his writings. By exposing the theoretical framework of the eleven textual units in which the expression namely appears, we explicate how he distinguishes between the act of being and the correlative ontological notions (the being, the essence, the predicamental judgment being and common being). If « actus essendi » first designates a constitutive principle of being, it can also designate the corresponding abstract term of this perfection of being. The act of being is that by which being is being; however, it belongs, at the ontological level, to each particular being whereas at the conceptual level, the same term expresses that which is common to all beings. Extracts of the following texts have been translated in French for this purpose: Scriptum super Sententiis, Quæstiones de quolibet, Summa Theologiæ, Quæstiones disputatæ De potentia, Expositio libri De hebdomadibus and the Sententia libri Metaphysicæ.