Remarks on the Architecture of Brentano’s Philosophical Program

This paper is about Brentano’s philosophical program inVienna and the overall architecture that holds together the main parts of his philosophy. My point of departure is the recent literature on the unity of Brentano’s philosophy, which has sometimes been understood as a “system” in the spirit of Kant and his successors, for example.1 I am particularly interested in the research program that he began to develop during his stay in Würzburg and that he exhibited upon his arrival in Vienna, namely in his inaugural address at the University of Vienna (Brentano, 1929a) and in his Psychology from an Empirical Standpoint . The term “research program” is used in this study in a broad sense to reflect, on the one hand, the implementation of the reform of philosophy from an empirical standpoint (i.e., philosophy as a science), and on the other hand, the structural unity, or the architectonic, of Brentano’s philosophy as a whole. This idea corresponds to what philosophers have called the tree of philosophy, the system of science, the encyclopedia of philosophy, etc., the main idea being to account for the unity and systematic character of the different parts of philosophy. Brentano himself, in his habilitation thesis, occasionally uses the notion of “philosophical system” in relation to the research program he attributes to Aristotle and other philosophers (Brentano, 1867, p. 1). Brentano’s program is based on the project of a philosophy as science in which he seeks to account for the unity of the main branches of his philosophy, including psychology and metaphysics, which are its two main branches. The aim of this study is to inves-tigate, from a bird’s eye view, the main articulations of Brentano’s philosophical program.


Philosophy of the History of Philosophy
At the heart of Brentano's philosophical program lies his theory of the four phases in the history of philosophy, which makes it possible to understand how Brentano took a stand with respect to the main philosophical trends that prevailed in mid-nineteenth century in Europe, and to identify his main sources of inspiration in the history of philosophy. This theory is so central in his philosophical program that it has been said that it was for Brentano's own philosophy what the law of the three states was for Comte's positive philosophy. Its starting point is in the observation of regularities in the course of the history of philosophy and it is based on the assumption that one can identify within each of the three major periods of its history four phases, or moments. The first of the four phases is one of ascent, while the last three indicate its decline.
As Brentano explains in a lecture delivered in Vienna in 1894 under the title "Optimism and pessimism" and later published as "The four phases of philosophy" (Brentano, 1895), the first phase undergoes an ascending development and it is first characterized by the use of the scientific method in natural sciences which is "the only true method of philosophy" and the latter is considered the best way to "establish and maintain a connection with other sciences" (Brentano, 1895a, p. 3). The second criterion highlights the philosophers who give priority to theoretical interests over practical interests. These two criteria are in fact two of the fundamental principles of his philosophical program. The second phase marks the beginning of a decline because of the weakening of theoretical interests, its gradual replacement by practical interests, and a loss of rigor and precision in the treatment of philosophical problems. The fisette second phase of decline is a reaction to the first and is characterized by skepticism, which is symptomatic of a loss of confidence in science and knowledge in general. Finally, the third phase of decline is also a reaction to the previous two phases, and it consists in the "construction of dogmas" and in the invention of artificial means in order to gain direct access to knowledge on the basis of principles which are devoid of any empirical foundation and rely instead on mystical intuitions. Whatever the value of this theory on which this philosophy of history is based, it is nevertheless decisive for identifying Brentano's closest allies and his historical sources of inspiration in philosophy. It also helps to understand the diagnosis he makes on the state of philosophy at this time. His description of the fourth phase as one of extreme decline applies a fortiori to the state of German philosophy when Brentano began to study philosophy and it aims at justifying his critical diagnosis on the philosophy of German idealism in the mid-nineteenth century (see Brentano, 1929cBrentano, , 1878. The two criteria underlying this theory are certainly important in the evaluation and taxonomy of the main philosophical trends in the history of philosophy, but they are not the only ones. For the great philosophical figures that are associated with the ascending phase in the three main periods in the history of philosophy-namely, Plato and Aristotle in Antiquity, Albert the Great and Thomas Aquinas in the Middle Ages, and Descartes, Leibniz, and Locke in modern philosophy-provide new criteria and testify to Brentano's efforts in advocating a philosophy that is in continuity with empirical sciences. Brentano further believes that, from a strictly philosophical point of view, these are the only philosophers worth studying.2 Despite his harsh diagnosis of the state of philosophy in mid-nineteenthcentury Germany, Brentano considers his time to be a transitory phase, and believes that philosophy is experiencing a certain renaissance. Brentano seems to have seen in the positivist treatment of philosophy the signs of an ascending phase in the history of philosophy succeeding the decline of idealistic systems and thus renewing the culminating moments in the history of philosophy to which philosophers such as Aristotle, Thomas Aquinas, Descartes, and John Locke, for example, belong. This is confirmed by Brentano in his article on Comte where he claims that his time is ready for "a positive treatment of philosophy": 2 In his inaugural lecture in the Philosophical Society of the University of Vienna entitled "The method of historical research in the field of philosophy," Brentano introduces several new aspects of his philosophy of history and proposes different methodological options for historical research and the interpretation of philosophical texts. Brentano claims that only philosophers have the skills and competence to deal properly with the history of their discipline. It is the task of our times to turn anew to a positivist attitude to philosophy. This task of returning to the positive spirit has largely been recognized, and we can see, here and there, a beautiful start which, in part, revives the lofty heights of the past and, in part, employs the advances of the natural sciences. brentano, 1869, p. 132 This passage contains a clear diagnosis of the state of philosophy at that time and the requirement for an in-depth reform of philosophy that Brentano conceives of as a return to the positive spirit that characterizes English empiricism and Comte's positive philosophy. Brentano provides a new confirmation in 1875 in his review of the work of his brother-in-law Théophile Funck-Brentano (1859)-a book that has been largely influenced by Comte's positivist sociology-in which Brentano (2011) compares the place of Comte in contemporary philosophy with that of Descartes in modern philosophy and in which he clearly suggests that Comte's positive philosophy, like British philosophy which it has influenced, marks the beginning of an ascending phase in the history of philosophy.

Philosophy and Science
Brentano has been the advocate of a reform of philosophy and the witness of a "renaissance of philosophy as science" (1929c, p. 131), by analogy with the status that philosophy acquires in ascending phases of its development, which presupposes that it establishes essential links with empirical sciences. This is confirmed by Brentano at the very beginning of his Psychology, in which he emphasizes the close relationship between his psychology and natural sciences, and explains that this relationship is motivated by his project to lay the foundations of a psychology as an empirical science. He claims that in philosophy, one must strive to achieve "what first mathematics and then physics, chemistry, and physiology have already achieved, i.e. a core of generally accepted truths capable of attracting to it contributions from all other fields of scientific endeavor" (Brentano, 2009, p. xxv). Brentano's philosophy is a philosophy of experience, and as such, it is closely related to empirical sciences. We can draw several parallels between philosophy and science in Brentano, and, first of all, with regard to the method which, as the early Brentano already emphasized in his fourth habilitation thesis (Brentano, 1866), is the usual inductive method employed by the empirical sciences and which philosophy ought to use. Another important parallel is the notion of phenomena, which fisette constitutes the primary object of philosophy and natural sciences. Brentano maintains that the world of phenomena is divided into two large classes, whose study falls within the domains of psychology and natural sciences. Physical phenomena such as sound, heat, color, etc. are the primary objects of sensory perception and the objects of the natural sciences, as opposed to mental phenomena such as hatred or shame, desire, and will, which are the objects of inner consciousness. Between these two classes of phenomena, there is an asymmetry, as Brentano shows in the first chapter of the second book of his Psychology, in which he examines a series of classification criteria and shows that the properties of a class are heterogeneous and irreducible to those that characterize the phenomena of the other class. Among these properties, let us mention space, which is an attribute of physical phenomena to the extent that phenomena in the visual field, for example, necessarily appear to us as extended. Brentano argues that one cannot say of the objects of outer perception that they are in reality as they appear to us, contrary to mental phenomena whose reality is justified by the evidence of inner perception. As Brentano explains: "We have no experience of that which truly exists, in and of itself, and that which we do experience is not true. The truth of physical phenomena is, as they say, only a relative truth" (Brentano, 2009, p. 14). Physical phenomena are merely "signs of something real, which, through its causal activity, produces presentations of them" (Brentano, 2009, p. 14) and as signs, all they are capable of achieving is "to tell us only about certain physical phenomena which are caused by the same unknown X" (Brentano, 2009, p. 45). But we cannot even conceive of what the realities, to which these phenomena refer, are in themselves.
Despite the importance of phenomena in his philosophy, Brentano clearly dismisses the form of phenomenalism associated with positivism. Brentano advocates instead a form of critical (or indirect) realism according to which, although the world is given to us and accessible only by means of the contents of our sensory experience (i.e., phenomena), the external world exists independently of the way one experiences it. And even though physical phenomena are mere signs, these signs refer to an actual reality whose action produces their presentation. Admittedly, we do not have direct access to the realities to which physical phenomena refer, and our knowledge of these realities is limited to the correlations that can be established between these phenomena and the external causes of sensations manifested in sensations. However, Brentano considers that, while science does not pretend to know the absolute nature of the world, it nonetheless attributes to it forces capable of producing sensations, and it is in this context that he makes the connection between his notion of force and Mill's "permanent possibilities of sensation" (Brentano, 2009, p. 75f.; see Fisette, 2018).
Our knowledge of the world is thus limited to relations between phenomena, or more precisely, to relations of succession and resemblance which link phenomena to each other. The main task of science consists in formulating the general laws which govern these relations. To use Brentano's favorite example, when a scientist tries to explain why one body attracts another, he does not search for an occult property belonging to the ultimate nature of gravity as the traditional explanations of similar phenomena would have it. It only relates phenomena with each other by means of a law, and in this case by the law of gravitation. This is how scientific explanations work for Brentano. The kind of explanations one is entitled to expect in the field of philosophy is not fundamentally different from that of natural sciences, as Brentano confirms in his inaugural address in Vienna. In this address, one of the important tasks he assigns to the philosopher and the psychologist consists in subsuming, on the basis of the observation of singular facts, the relations between singular psychical phenomena under general laws (Brentano, 1929a, p. 94 f.). It is not different in the field of metaphysics, in which the philosopher must use the method of the natural sciences and seek to discover "more general truths, valid uniformly both in the field of psychical and in that of physical phenomena, and therefore in the universe as a whole" (Brentano, 1929a, p. 96) while avoiding getting into the search for "absolute knowledge." This limitation of our knowledge of the realities of the outside world is reflected in the thesis of the relativity of knowledge, which has been also advocated by philosophers like W. Hamilton and John Stuart Mill, for example (see Fisette, forthcoming). Brentano conceives of it both as a limitation of our knowledge of transcendent realities and as the relational character of our knowledge. Although we do not have direct access to the things in themselves (to causes of phenomena), and although our knowledge of them is consequently substantially limited, these realities nevertheless exist, however, independently of the knowledge that we have of them. The relativity of knowledge has nothing to do with the metaphysical positions advocated by Kantianism or positivism, which make transcendent realities dependent on subjective conditions and thus commit themselves to one form or another of idealism. Furthermore, the relativity of knowledge must not be confused with scepticism. It is simply the direct consequence of Brentano's critical realism.

Classification of Sciences
Brentano maintains that there are three main branches of science: natural sciences, psychology, and metaphysics (Brentano, 2009, p. 4;1929d, p. 96;1925, p. 51). fisette Psychology is the science of mental phenomena, natural sciences study physical phenomena, while the task of metaphysics is to discover general truths non-matching quotation mark "which, uniformly valid for the domain of the physical as well as for the domain of mental phenomena, are valid for the universe as a whole (Brentano, 1929a, p. 96). Psychology and metaphysics are philosophy's two main axes and we shall see that the latter is distinguished from natural sciences mainly by its object. The general structure of Brentano's division of sciences is relatively well illustrated by the following diagram: This classification is based on some important distinctions, in particular those between natural sciences and philosophy, between theoretical and practical sciences, and between the three normative sciences, i.e. ethics, logic, and aesthetics. The diagram further shows that these three philosophical sciences are rooted in descriptive psychology. Metaphysics and psychology constitute the two main branches of philosophy, which gives psychology the status of philosophy of mind, i.e., the status of a philosophical discipline to which belong the conceptual analysis of thoughts. But since psychology belongs to the system of science as well, as we shall see, it appears to have the dual status of a natural science and of a philosophy of mind as Brentano will later recognize in his lectures on Psychognosie. This last remark introduces the theme of the classification of sciences by Brentano. Where Comte exerted a lasting influence on Brentano is undoubtedly in the classification of the sciences which he elaborated at that time and which he presented upon his arrival in Vienna in 1874 (see Fisette, 2018). Brentano maintains that theoretical sciences form a unity which is determined by relations of dependence which all sciences maintain with each other, and that they form a whole of which they are the parts. They are interrelated in such a way that they form a scale of sciences whose order is determined by the degree of generality and simplicity, and by the logical dependence of phenomena on or with respect to each other. These are also the three main criteria in his classification of sciences: simplicity, generality, and relative dependence. Dependence derives from the phenomena themselves, i.e. from the degree of simplicity or generality of phenomena, as shown by Brentano's classification of sciences. Brentano's classification differs from Comte's in that he replaces Comte's sociology by psychology, arguing that sociology is merely a branch of psychology, and that the social phenomena it studies belong essentially to mental phenomena (Brentano, 1929a, p. 100). Thus, psychology represents, with mathematics, one of the two poles in Brentano's classification of sciences: "Mathematics considers the most simple and independent phenomena, psychology those that are most dependent and complex" (Brentano, 2009, p. 22). Physics, chemistry, biology, and physiology are located in between these two poles (Brentano, 1929a, p. 93).
These sciences form a series extending from the most abstract to the most concrete sciences. The ordering of this series is conditioned by logical relations of dependence from the most complex to the simplest sciences, the simplest and most universal being mathematics, which is the only science that is autonomous with regard to the other sciences in the Brentanian system of science.
This scale shows that physiology immediately precedes psychology, and Brentano admits that psychology depends on the physiology of senses insofar as, on the one hand, mental states are given to us only in relation "with organisms and in their dependence with certain physiological processes" (Brentano, 1929a, p. 94). On the other hand, sensations are an important source of psychical phenomena belonging to the simplest class of mental phenomena, namely presentations, which are directly related to the physical phenomena which are its primary objects. That is why Brentano maintains that it is impossible to separate both of them absolutely. This dependence can be explained, first of all, by the scientific laws that are presupposed by psychology. For physical phenomena take place under the influence of mathematical laws, chemical phenomena under the influence of physical laws, phenomena of physiology under the influence of the latter while psychological phenomena are in turn indirectly influenced by all these laws. On the other hand, mental phenomena are directly influenced by the laws governing the sensory organs, i.e., by physiological laws.
This scale of sciences is essential to understanding why sciences such as psychology and physiology do not evolve at the same rhythm as other sciences, and why physiology and psychology lagged far behind in their development in Brentano's time compared to other sciences that precede them in this scale (Brentano, 2009, p. 18). Not only does psychology lag significantly behind the other sciences, but the status of the laws on which it is founded is not the same as that which they have in other sciences. For the laws of psychology, unlike the laws of physics, for example, are empirical generalizations, acquired by induction, and they therefore remain incomplete and inaccurate in comparison with the laws of the sciences of physical phenomena and especially mathematical laws which are paradigmatic of sciences. That is why physiology, as a science of physical phenomena, is indispensable to the development of psychology insofar as "the discovery of the really ultimate laws of the succession of mental phenomena is possible only on the basis of physiological facts" (Brentano, 2009, p. 47). This explains a fortiori the impossibility of mathematizing psy-chology by subordinating the complex domain of mental phenomena to the laws of mathematics. For Brentano, this seems to be a necessary condition for a discipline which claims the status of science. That is why Brentano considers psychology to be science in the making, or as a science of the future, even if he is confident that psychology will one day acquire the full status of science that it claims for itself.

Psychology
The place of psychology in this classification raises several other questions, including that of its status as science. Brentano conceives of it as a science "without a soul" whose field of study is delimited by psychical phenomena, i.e., by presentations, judgments, and emotions, and to which one has access by means of inner perception. Because of its object and the mode of access to its field of study, psychology differs from all the other sciences, and, first of all, from natural sciences whose object of study are physical phenomena. And the notion of intentional inexistence, by which Brentano characterizes mental phenomena, is also the main criterion for the classification of phenomena into two classes. In light of these important differences between psychology and natural sciences, and between the two classes of phenomena, the question arises concerning what it is that makes psychology an empirical science in the same way as the other sciences which precede it in the system of sciences and which, as a science limited in its development, it presupposes. Here again, the comparison with Comte's positive philosophy can be useful because the definition of science that Brentano uses in his Psychology is very close to that which he attributes to positive philosophy in his article on Comte. That being said, psychology constitutes the philosophical science par excellence and the phenomena it studies constitute the most noble object in the evolution of science and humanity in general. Brentano writes in this connection that "there is hardly another branch of science which can be placed on the same level with psychology unless perhaps it is one which merits the same consideration on the grounds that it is an indispensable preparatory step toward the attainment of psychological knowledge" (Brentano, 2009, p. 15). And psychology owes this privileged status to the fact that its object not only constitutes the things which are "most our own" but also that they are incomparably more "beautiful and sublime" than any phenomena studied by empirical sciences (Brentano, 2009, p. 15). However, it is known that after the publication of his Psychology, Brentano made substantial changes to several aspects of his psychology, the most impor-fisette tant of which occurred in his lectures on descriptive psychology which he taught in Vienna between 1887 and 1892. The first distinction occurred within psychology between descriptive and genetic psychology, a distinction which corresponds to that in the field of biology between anatomy and physiology, anatomy being to the description of the organism what physiology is to its function and to the explanation of the functional mechanisms of the human organism, in particular the functions of the nervous system. These two branches of psychology have complementary but distinct functions: genetic psychology seeks to explain the phenomena that descriptive psychology describes and analyzes. Genetic psychology is closely related to physiology in that it deals with laws "according to which phenomena appear and disappear" (Brentano, 1895a, p. 34). His main task is to inductively establish the general laws governing the succession of mental phenomena in order to explain them. This branch of psychology is outward-oriented, i.e., oriented towards physical phenomena by means of outer perception, while descriptive psychology deals with the properties of mental phenomena which are only accessible through inner perception. This distinction makes it possible to dispel an ambiguity surrounding the dual status of psychology in the 1874 Psychology both as a "backward" natural science and as a philosophy of mind, i.e., as one of the two main axes of philosophy. This clearly stands out in the following diagram which takes into account the descriptive-genetic distinction within Brentano's psychology.
One of the important theses of these lectures on Psychognosie is that descriptive psychology has a methodological priority over genetic psychology in the sense that any explanation presupposes the description and analysis of the phenomenon to be explained. For example, when one undertakes to explain a phenomenon such as consciousness or why someone behaves in such and such a way and in this or that circumstance, one must first inquire what the nature of the phenomenon to be explained is, and this is why one must provide a preliminary analysis and description of the explanandum. If one does not respect this methodological rule, when one seeks to grasp the genesis of phenomena without having previously analyzed and described them accordingly-for example, as if one wanted to practice physiology without a preliminary study of anatomy-one then commits a hysteron-proteron, i.e., one places the cart before the horse. This is one of the criticisms that Brentano raised against scientists like Wundt, Helmholtz, Fechner, Comte or Horwicz (Brentano, 1929d, p. 79) insofar as they exaggerated the services that physiology, even phrenology (in Comte), could offer to psychology both methodologically and in the knowledge of mental phenomena.

The Three Main Philosophical Sciences
The three main philosophical sciences are rooted in psychology. Indeed, the three normative sciences-i.e., logic, ethics, and aesthetics-maintain a close relationship with psychology because their laws and theoretical contents depend entirely on psychology. These three practical sciences are based on Brentano's classification of mental phenomena. In fact, Brentano distinguishes, in the class of psychical phenomena, three subclasses of mental phenomena: presentations, judgments, and emotions. The principle of this classification is borrowed from Aristotle, who based his classification "on the different relations that mental activities have to their immanent objects, or their different kinds of intentional inexistence" (Brentano, 2009, p. 152). This difference in the intentional relation to objects lies in what he calls in his Psychology "modes of consciousness" (Brentano, 2009, p. 149), forms, or attitudes, all of which refer to stances toward objects or, more precisely, ways in which one becomes aware of her objects. Brentano's classification of psychical phenomena is entirely based on the three general modes through which consciousness comes into contact with its objects: the presentational, the judicative, and the volitional or emotional modes. Moreover, there exists between these three classes of phenomena an order which is similar to that which prevails in the classification of sciences. For the fisette principles that determine this order are indeed the same as those Brentano uses in his classification of sciences, namely "the relative independence, simplicity and universality of the classes" (Brentano, 2009, p. 207). Presentation is the simplest class, as it is independent from the classes of judgment and emotions, and it is more universal "insofar as the only way in which the primary object is necessarily and universally present in consciousness is with the kind of intentional inherence peculiar to presentations" (Brentano, 2009, p. 207). Judgments and emotions, on the other hand, are more complex, and are dependent upon the class of presentations. Brentano speaks of a one-sided dependency relation between higher-order acts and presentations in the sense that any emotion such as anger presupposes a judgment on the state of affairs that arouses anger and a presentation of the latter. From this insight follows some fundamental rules of psychology, the most important of which being that all psychical phenomena "are either presentations or they are based upon presentations" (Brentano, 2009, p. 65). It follows from the founding character of the class of presentations that "nothing can be judged, desired, hoped or feared, unless one has a presentation of that thing" (Brentano, 2009, p. 61). Brentano believes that these three classes contain the three fundamental modes of the intentional relation to objects and that they are therefore irreducible to one another. And this classification is itself the foundation of that between the three main normative sciences.
Aesthetics, logic, and ethics are the centerpiece of Brentano's philosophical program because they are the three basic philosophical sciences. Brentano recalls that it was on the basis of the results of his research in psychology that he was able to reform logic, ethics, and aesthetics, and he maintains that they are inseparable inasmuch as, if they were separated from psychology, they "would necessarily dry up as a separate branch from the tree trunk" (Brentano, 1895a, p. 40). The following diagram helps to situate this ramification of psychology into three practical sciences for Brentano's research program: In a similar way to his classification of sciences in which physical phenomena link theoretical sciences to one another, in the classification of psychical phenomena, the three classes of mental phenomena bind together these three practical sciences and constitute the primary object of Brentano's three main philosophical sciences.
They are practical sciences because they are governed by the laws of psychology which they apply to their respective object of study. All other branches of philosophy, including political science or sociology, for example, depend on psychical phenomena and the laws of psychology (Brentano, 1876, p. 94).
This ramification involves several other fundamental aspects of Brentano's philosophy that add to the complexity of his philosophical program. The first is his theory of knowledge, because of the important role of the evidence of fisette inner perception in the justification of knowledge. A second one lies in its axiology because of the importance of values in the conception of these sciences. Beauty, truth, and goodness are linked to each class of mental phenomena: aesthetics as a science of beauty, logic as the science of truth, and ethics as the science of good. Finally, there is the normative dimension of these three practical sciences and the question of correctness (Richtigkeit), i.e., the question as to whether the stance that one must take toward an object is correct or incorrect. This normative component enters into the definition of the object of these three sciences: aesthetics as the science of correct presentation and taste, logic as the science of correct judgment and ethics which, as "the practical discipline which teaches us the highest ends and the choice of means to achieve them" (Brentano, 1959, p. 88), is related to correct choices and correct voluntary action.

The Place of Metaphysics in Brentano's Program
The last point that the classification of the sciences presented above brings to light is the place of metaphysics in Brentano's philosophical program. The next question pertains to the way metaphysics is related to natural sciences and how it fits with this overall framework. As I said, metaphysics constitutes the second main branch of philosophy.
This diagram indicates that, despite the central place of psychology in Brentano's thought, one cannot underestimate the place of metaphysics in his program. Brentanian metaphysics is one of the three sources of knowledge alongside natural sciences and psychology (Brentano, 2009, p. 4), and its task is to discover the general truths that are valid both in the field of psychical phenomena and in that of physical phenomena, such as psychophysical laws, for example. That is why Brentano's metaphysics, by virtue of its method and of its object of study, is intimately linked to natural sciences and is subdivided into several different branches. As the science of being qua being, metaphysics must fulfill several other tasks that are related to the four fields corresponding to the divisions of metaphysics in Brentano's lectures on metaphysics, namely transcendental philosophy, ontology, theology and cosmology.
The primary task of the first branch of metaphysics is to study the conditions of possibility and the justification of our knowledge of the external world. It is to this area that the discussion on critical realism belongs, his criticism of the Kantian doctrine of the thing in itself, his criticism of ancient and modern skepticism as well as his arguments against phenomenalism, for example. The second branch of metaphysics, which is the subject of Brentano's dissertation, is ontology, which deals, among other things, with categories, substance and its accidents, and the theory of relations to which Brentano and his students have always granted a great deal of importance. The third branch of metaphysics is theology, the main topic of which is the search for a principle of the universe and for the proofs of the existence of such a foundation. It is to this branch of metaphysics which Brentano's numerous studies of religion, the proofs of the existence of God, and theism belong. The last branch is cosmology, to which belong the issues Brentano discussed in his talk "Die Gesetze der Wechselwirkung der Naturkräfte und ihre Bedeutung für die Metaphysik", for example, the questions of whether "there exists in the living nature a real or merely apparent teleological order" (Brentano, 1929d, pp. p. replaced by pp., ok? 71, 74); whether there exist several laws; and whether "the law of causality and its so-called a priori fisette character", "the law of the reciprocal action of the forces of nature", and "the law of conservation and transformation of the force [are] valid in general absolutely" (Brentano, 1929d, p. 74), etc.
The following diagram (see Chrudzimski, 2004) indicates, in addition to the four branches of metaphysics, the main branches of ontology: As one of the two axes of his philosophy, metaphysics is therefore at the heart of Brentano's program and its specific task consists in the search for truths and general laws that apply equally to the field of inner experience and to that of outer perception, and therefore to the universe as a whole: In the same way, they would have undertaken to discover, in the field of metaphysics, more general truths valid uniformly, both in the domain of psychical phenomena and in that of physical phenomena, and therefore in the totality of the universe. They would also have been satisfied with the relative knowledge and would no longer have gone astray in aspiring to absolute knowledge, in the field of mere inconceivability. brentano, 1929a, p. 96 This excerpt raises a question on which Brentano has always placed a great deal of importance: namely, how does one justify the importance of a discipline that, since Kant, seemed to be falling apart? Brentano is fully aware of this (see Brentano, 1929e, part i;Brentano, 2016) and he clearly dissociates his metaphysics conceived from an empirical point of view from the "exuberant speculations" of this other metaphysics, which he compares with Mephisto's description of it in Goethe's Faust. The philosophers who indulge in these metaphysical speculations obviously belong to the terminal phase of philosophy's decline and Brentano's target is here again philosophers like Plotinus or Schelling, who aspire to absolute knowledge in the sphere of mere inconceivability (Brentano, 1929d, p. 96). This bad metaphysics is prejudicial to this branch of philosophy whose task is to seek the ultimate foundations of things and to look into the most general questions which do not belong to any other existing science or discipline of philosophy. But metaphysics must be reformed in the same way as other disciplines that contribute to his philosophical program.
This distinction between two meanings of metaphysics allows us to better understand why Brentano believes that, in contradistinction to many contemporary philosophers, metaphysics must be reformed and not destroyed or eliminated (Brentano, 2016, p. 36). This reform is based on the idea of a metaphysics "from an empirical point of view", i.e., as a science which, to be the most general of all sciences is nonetheless in continuity with sciences such as physiology, chemistry, and physics, on which it depends. Conversely, metaphysical questions are not just philosopher's inventions, they are at the heart of the activities and research of working scientists, as Brentano clearly demonstrates in his lecture "Die Gesetze der Wechselwirkung".
Moreover, contrary to traditional metaphysics, which is constructed a priori, Brentano's metaphysics is based on experience. It "starts from below," which means that it proceeds, just as any empirical sciences, from the particular to the general. Metaphysics specifically follows the method of the natural sciences and in Vom Dasein Gottes (Brentano, 1929e, p. 217f.), Brentano prescribes the inductive method and the theory of probability in the formulation of proofs of God's existence. And this way of arguing in the field of metaphysics, for example, is peculiar to Brentano and this is how he stands out from his predecessors. And that is why his proofs rely heavily on sciences: from the ether to the curvature of space, through the laws of gravitation, the hemispheres of the brain and genetics. In "Die Gesetze der Wechselwirkung", for example, he makes an argument used at the time by scientists like W. Thompson, R. Clausius and later A. Fick, based on the second principle of thermodynamics, i.e., entropy, as a support for the cosmological proof of the existence of God. In summary, this proof is based on entropy and starts from the idea that the world's entropy is continuously increasing and that the actual state of the world's entropy is not very high; therefore, the world must be relatively young and so must have a fisette beginning. It follows from the fact that it has a beginning that it was created and that if it was created, God is necessarily its creator.
Another important topic related to Brentano's metaphysics is theism. In his article "Atheism and Science," he undertakes to refute the thesis of the incompatibility of theism with a philosophical program based on the idea of a philosophy as science. In this article and his lectures on metaphysics, he seeks to refute the arguments of those who see a principle incompatibility between theism and Darwin's theories. Most of the teleological proofs in his book Vom Dasein Gottes are a discussion of Darwin's theories on evolution and natural selection (Brentano, 1929e, § §301-350). In "Atheism and Science," Brentano reproaches his interlocutor for not explaining the meaning of this pseudoincompatibility he sees between Darwin's theory of evolution and theism, and thus leaving unanswered the question as to whether evolution has a beginning and an end. It is in this context that he again evokes the law of the reciprocal action of natural forces and refers to the works of Helmholtz and A. Fick as he did in his lectures of 1869 on the same theme. Brentano also addresses the objection that theism threatens the progress of science and that the conception of the atheistic and materialistic world would have the advantage of being a monism, while the theistic vision is committed to a form of dualism. To this last objection, Brentano replies that only theism is truly monistic "insofar as it derives all phenomena from an ultimate single cause" (Brentano, 1873, p. 864).

Final Remarks
These general remarks should be enough to show that Brentano was guided by a research program in philosophy based on a complex architecture that underlies its unity. To conclude, I would like to add a few remarks on another important question regarding Brentano's philosophical program, i.e., its justification. I claim that this justification rests on Brentano's philosophy of history and in his theory of the four phases in the history of philosophy that was discussed at the beginning of this study. There are several important connections between this theory and Brentano's philosophical program. The three most important for my own purposes are the following. As I said at the outset, like any other theories which figure in this program, Brentano's philosophy of the history of philosophy is based on laws, as he explains throughout his works. We saw above that Brentano stresses the nomological character of his theory of the four phases and speaks of "constant historical law" (Brentano, 1968, p. 37), and "fixed laws" (Brentano, 1876, p. 21), by which the gradual decline of philosophy takes place. The term "law" also occurs in his lectures on the existence of God, and in the 1894 essay on the four phases in which he argues that regularities in the course of the history of philosophy testify to the presence of historical laws which underlie this historical process (Brentano, 1895b, p. 48).
Moreover, this theory is based on two criteria by which one determines whether a philosophical program belongs to an ascending or a declining phase: first, the method of natural sciences, and second, the primacy of theoretical over practical interests. These two criteria obviously correspond to two characteristic features of Brentano's philosophical program. More importantly, his philosophy of history provides a justification for his research program to the extent that the theory of the four phases justifies Brentano's optimism with respect to the future of philosophy at a time of decline of idealistic systems. For it makes it possible to understand both Brentano's attitude toward the state of decline of philosophy at the time and his optimism and confidence in the future of philosophy. That is why Brentano's theory of the four phases provides at the same time a form of justification for his own philosophical program. Brentano has always considered that "the golden age of philosophy" is not past, but rather to come (Brentano, 1929d, p. 40;see Werle, 1989).