S ubStance , change and matter in the a nalogieS of e xperience of K ant ’ S C ritique of P

The subject discussed in this article is primarily the concept of substance ( Substanz ), but additionally, also debated are the concepts of change ( Wechsel ) and matter ( Materie ), both closely related to the first. All three are studied in the Transcendental Analytic and specifically in the Analogies of Experience in the Critique of Pure Reason. Since Roman times, when the concepts of “hypóstasis” and the Aristotelian category of “ ousía” by “substantia” were first translated, the term substance has been taken on a long and intense journey throughout the history of philosophy

The subject discussed in this article is primarily the concept of substance (Substanz), but additionally, also debated are the concepts of change (Wechsel) and matter (Materie), both closely related to the first. All three are studied in the Transcendental Analytic and specifically in the Analogies of Experience in the Critique of Pure Reason. Since Roman times, when the concepts of "hypóstasis" and the Aristotelian category of "ousía" by "substantia" were first translated, the term substance has been taken on a long and intense journey throughout the history of philosophy.
In the KrV (Critique of Pure Reason) there are mainly two moments to consider regarding the substance. Firstly, the transcendental Analytic, which studies the substance as the first category of relation, its scheme and its functioning in the first of the Analogies of Experience. Here Kant explains its objective or phenomenal meaning.
Secondly, the transcendental Dialectic must be taken into consideration, starting with the Paralogisms, because there are posited ontological limits to the category of substance considering that it is not applicable to "I think" or "Transcendental Apperception", because the transcendental subject has not the mode of being of the substance, but it is an ideal and a logical-transcendental action. This calls into question contemporary criticisms towards the socalled "modern" subject, thus levelling the philosophical proposals of modernity in relation to subjectivity and matching all of them with the Cartesian res cogitans. Kant's transcendental I is not a substance 2 , not a res, neither immanent nor transcendent to the world, nor is it a thinking monad, nor the mode of an absolute single substance, as proposed by Spinoza. It is the ideal action of cognise the world; its unity does not have the quantitative attribute of the substance, but the qualitative property of the transcendental action, which unifies both the manifold of every object and of the whole experience 3 , which is in continuous expansion following the guiding thread of the interaction (Wechselwirkung).

1.
The substance appears in the table of categories as the first of the categories of relation. These are double categories, and the category of substance goes together with the category of accident 7 . The other relation categories are those of cause and effect and that of interaction between substances.
The categories of relation systematically follow those of quantity and quality. It is thanks to the former that the sensible form and matter of the appearance respectively are strictly demarcated according to the rules of the transcendental imagination (schemes) and understanding (categories), thus configuring every object in its singularity. Objects are defined in their time and space by means of the categories of quantity and their schemes, and the empirical content of every appearance is understood as real by virtue of the categories of quality and their schemes.
After this process of delimitation and quantitative-qualitative interpretation of all appearances, the work of positing them in relation to each other begins with two purposes, firstly, to place them among themselves in the common time and space, that is to say, in the objective time and space, and, secondly, to establish their relations of dependence (of heteronomy) on each other. That is the task of the relation categories, their schemes and their principles, which also operate based on the categories of quantity and quality, and it is because of them that a link is built, an interconnection between all appearances, a unified experience with all of them, a "natura formaliter spectata" 8 . "By nature (in the empirical sense) we understand the combination of appearances as regards their existence, in accordance with necessary rules, i.e., in accordance with laws. There are therefore certain laws, and indeed a priori, which first make a nature possible; the empirical laws can only obtain and be found by means of experience, and These rules are forms created by the transcendental subject. They are questions that the subject poses from himself, from its spontaneity, to the sensible appearances to which they must respond: what space they occupy, what time, what is their cause, what interrelation do they have, etc. These questions are not based on a particular experience, but they configure all empirical cognition, in the same way that grammar structures all use of language, without being able to give a reason as to why those rules and not others (facticity of form) 10 . They are questions or regulated ideal actions of the subject, because it is only in this way, according to Kant, that those idealities can have universal and necessary validity for every object and every subject, and it is not possible for an object not to fulfil them 11 , because, if it did, it would not be an object for us, we would not understand it objectively, would not know how to place it, to order it within the experience.
In addition, it must be taken into consideration that objects are unable to offer or transfer concepts, idealities to us, because they do not possess them, they can only cause physical effects. Cognition is an ideal elaboration of reality made by the subject: when I cognize an object, for example a tree, I do not really transform it, I do not water it, I do not prune it, I do not cut it, I do not transfer it to another place, nor I do not burn it, etc., but I introduce it into the ideal field of cognition. It is only in this way that the subject is able to discover the reality of the world and turn it into something for him; cognition or consciousness is an ideal sphere opened by self-consciousness, not by objects. Here, therefore, is the second point, ie, that the category of substance, like the others, is ultimately an ideality, not an ontic law of objects in themselves, but a transcendental need for objective understanding of the world, a subjective strategy for the ordering and interpretation of the experience, to "spell out" the appearances and "be able to read them as experience" 12 . Other than that, the categories only have a logical, albeit not objective, meaning 13 .

3.
Consequently, to become cognition, transcendental ideality implies and requires, in turn an empirical realism, something sensibly given, otherwise all that is left are mere empty idealities, without an objective scope; that also happens with the category of substance. Furthermore, neither the "I think" nor its transcendental idealities would exist if the objects of the world did not respond to them in any positive way, at least to a sufficient extent to enable the management of objectivity 14 , as they are actions and forms of objectification. They are ways of objectively elaborating and ordering the given sensible experience, and to cognize the world, so that the I knows about it. For example, all theories about the multiple subatomic particles become valid when they are somehow physically detected; otherwise, the theory or idea about a particle would be a mere hypothesis still empty, without objective validity.
For this reason, such transcendental forms or idealities would not occur without what is given in the sensible experience, without a real world to cognize. The rules are not given by the objects, but they would not exist without a positive response from the world and, in that context, it can be said that they also depend on the objects. However, (1) objects cannot be considered things in themselves in a transcendental sense, as they answer our questions, our cognitive forms, and in that respect the form they present is dependent on ours, on our questions, and we would not know if they could respond to others, that is, to other knowing beings that acts with other transcendental forms (facticity of our forms, especially time-space).
(2) In known things, time, space and categories are as empirically real as transcendentally ideal 15 ; if they were not ideal, the I could not process the objectivity of the world and discover it, but if they were not to correspond to the empirical reality of the objects, then those forms would be empty, they would not have objective validity and, in the end, they would disappear along with the subject of cognition. Therefore, (3) when we go beyond the experience, questioning the unconditioned: the soul as a simple and immortal substance, or the world as a whole or God, we are only left with mere idealities that fail to provide us with cognition of what is real, because of the absence of that Real. This is what Kant studies in the transcendental Dialectic.
It could be possible the world not to exist at all, and that would not be contradictory since existence is not another predicate among the predicates of a thing but the absolute positing of the thing with all its possible predicates, as Kant clarifies in his work The Only Possible Argument in Support of a Demonstration of the Existence of God 16 , and again explains in the Critique of pure reason, arguing against the ontological argument about the existence of God 17 . The modal category of existence is different from the modal category of possibility because it also requires that something should be given empirically. But if the world did not exist in any way, we as cognitive subjects would not exist either, as the transcendental I is not a transcendent substance that could exist without a world.
Transcendental forms are not empirical, nor are they divine forms that could materially and magically create their own world. The world could be different, have another form, and transcendental reflection, contrary to rationalism, starts with the facticity of a priori forms. But given that we exist as cognitive beings, there are good basis to assert, contrary to scepticism, that the world exists and that it is how we objectively cognize it, at least to a sufficient extent to manage ourselves within it, and our task is to constantly increase that cognition. Although the empirical cognition of the world is, or should be, in continuous progression, it is always based on an a priori transcendental structure because they are needed to understand and organize the experience. For example, it would be possible to say that everything in the world is predetermined, but only to the extent to which the cause of an appearance is found by means of the categories of causality and interaction, and insofar as this cause explains (always partially) that appearance. The categories of relation are regulative, they do not provide us with the object in intuition (contrary to what happens with the categories of quantity and quality), but they offer the rule to seek it 18 . Real cognition is always in fieri, in the spatial-temporal-causal continuum.
It may also be that chaotic states exist in the world, as it seems to be in black holes or at the time before the big bang. In that case nothing responds to anything persistent and therefore objective cognition would be impossible. 19 The category of substance does not state that there will always be something persistent in the world, as if by divine decree, but that the subject always needs something persistent in order to make objective cognition possible as well as -I would add -the real action of the subject and the subject itself. The category, and that includes the substance, is a transcendental requirement, not an ontic law of things in themselves. This allows an understanding of what is given, and thus a search for regularities begins, regularities that are real, constitutive and not simply "as if ", which is the case with teleology in nature, since that is not an object of intuition. There is always a search for persistence, change and dependence, and as these are found, objective cognition exists. But it is very possible that we ignore more than we know. A single category with nothing empirically given is not objective cognition: "Thoughts without content are empty, intuitions without concepts are blind" 20 . This is also the case with the category of causality, which does not give us the cause in intuition but initiates a search for it, and it only has objective meaning when the cause is empirically found. Consequently, it cannot be said that everything is determined, since the totality is not an object of experience, even not the totality of an object, because all real empirical experience is limited, and empirical cognition is always in fieri in the spatial-temporal-causal continuum. The categories without empirical experience are empty, unrealized tasks, forms without any objective content.
Thirdly, the category of substance also requires its empirical realism.

4.
"Now that which connects the manifold of sensible intuition is imagination, which depends on understanding for the unity of its intellectual synthesis and on sensibility for the manifoldness of apprehension" 21 . It is the scheme of the transcendental imagination that makes it possible to assign a sensible reality to what is demanded by the categories. The category does not apply directly to the empirical, it does so through the a priori forms of sensitivity, that is, through time and space. The same occurs in the category of substance, contrary to what Hume sought, as he wants apply it to an impression as the last criterion of reality, and required that an impression always remained present in order to designate it as a substance and because he did not find it, he disqualified it as a category 22 . The necessity is not in the impression, in the empirically given, since it offers us only the case, not the necessity, but it is situated in the transcendental requirement of understanding expressed in the a priori forms.
The objective application or use of the category goes, according to Kant, through an imaginative process or translation of the logical content of the category in time and space as a priori forms of sensitivity. In transcendental Schematism, Kant offers an uniquely temporal translation of the categories, so that "the scheme of substance is the persistence (Beharrlichkeit) of the Real in time" 23 , "for only this persistence is the ground for our application of the category of substance to appearance" 24 , since all modification is predicated on the persistent. The substance in the appearances is something that lasts (dauert) over time. In the appearances, this sensible persistence of the object corresponds (correspondiert) to the time considered as persistent and to always being the same, the same time, in its incessant flow, and since time itself is, as form of intuition, unlimited and cannot be perceived, it is the phenomenal substance, as sensible persistent what makes the perception of persistent time possible 25 and with it, the other two modes of time: succession and simultaneity 26 , that is, the determination and objectification of what changes and what exists at the same time (die Folge und das Zugleichsein), although other elements are also required to make other two determinations of time possible: "that which persists is the substratum of the empirical representation of time itself, by which alone all time-determination is possible" 27 .
But following the production of the passage of the Critique of pure Reason, second edition called "Refutation of idealism", Kant understood that all persistence also requires a space in which to persist, while empirical time always flows, and that it is that spatial persistence or matter 28 with its own temporality, namely, that of external objects or of the outer sense, which makes it possible to objectively determine the particular and different temporality of the representations of the inner sense. The argument of the first Analogies of Experience 29 starts precisely from that distinction between the temporalities of external objects, that can be persistent, and the representations of the inner sense, that are always successive and dependent on attention (Aufmerksamkeit) 30 . The persistent is necessarily a time-space appearance. That is why Kant concludes that the time of inner sense is not enough to assign objective reality to the categories, something he had previously believed and pointed out in his Transcendental Schematism (where the idea of transcendental aesthetics was followed, according to which the time of the inner sense was the time of all appearances), which he would have to rewrite, but that also required are the outer and spatial intuitions 31 and the temporality of these objects. So, "in order to give something that persists in intuition, corresponding to the concept of substance (and thereby to establish the objective reality of this concept), we need an intuition in space (of matter), since only space alone persistently determines, while time, however, and thus everything that is in the inner sense, constantly flows" 32 . The persistent leads us to something external and spatial, which Kant calls matter, "object of outer sense […] impenetrable lifeless extension" 33 , and this cannot persist in a mere impression of the inner sense, as claimed by Hume: "the concept of matter as substance is the concept of something mobile in space" 34 . And the same can be said of simultaneity, the scheme of the category of interaction, which also requires space, namely, that two or more objects occupy different spaces so that they can exist at the same time 35 . And that also happens with causality, the second category of relation, since it is what determines the successive temporality of external and extensive objects.
Fourth idea: the category of substance is applicable to the sensible persistent in time-space, where changes or accidents are inherent -that is its interpretation, application or objective translation, its possible empirical realism 36 . This persistence or duration of the appearance or object is the work of the imagination, which goes through the sensible manifold, takes it up and synthesizes it in a unity 37 , maintaining the differences, the consciousness of the different parts of the space, the different moments of time and the qualitative differences in that extension and temporality, and the object responds positively to that subjective action. It is the imagination that implements in time-space-qualities what is required by the category of substance 38 . The persistent that corresponds to the substance is gone through, taken up and combined by the subject thanks to the imaginative synthesis of the sensible manifold of an object and recognized reflexively by the concept or category of substance. The figurative synthesis of the imagination or imaginative scheme, and the intellectual one of the category (concept, understanding and Judgment) 39 , are acts of spontaneity of the transcendental subject, without whose spontaneity or action it would not be able to understand anything, and is not found in impression or perception (Wahrnehmung), which in contrast contain a pure manifold in random juxtaposition 40 .
From the concept of substance different meanings can be now identified. The logical meaning, where substance is the ultimate subject of predication that cannot become a predicate 41 . From the ontological perspective, or according to the modes of being, the substance is the substratum or support of its accidents or states (Zustände), not in the sense of the accident being something in itself, but "only through the way in which the existence of a substance is positively determined" 42 . Transcendentally, it is required that this existence occurs sensibly in time-space, specifically as something that persists and lasts, while accidents change, as the support or the substratum of the changes in the world is the persistent. That persistent then appears physically or ontically as an object, specifically as an external object of the world, that is, as a material body, because in the inner sense there is only a constant flow of representations, there is nothing that lasts, as Hume already indicated when he said that no impression remains, and therefore no substance can be found in that sphere, because the substance also needs space. Hence, for the temporal determination of the inner sense and its representations, it is necessary to have a relation with the extensive objects of the outer sense and its temporality, ordered though category of causality, which was demonstrated by Kant in his "Refutation of Idealism" 43 .

5.
In the transcendental Analytics of the Principles, the forms previously studied in the Critique are put through a synthetic process: the pure forms of sensibility, the categories and their schemes. With them the first judgments or principles about the entities as objects are formed. In this way the category of substance and its scheme are also put into practice, and its objective meaning and scope are determined more precisely.
In the first two principles, namely, in the Axioms of Intuition and in the Anticipations of Perception, transcendental and regulated syntheses of the spatial and temporal forms, and the sensible content or reality of each appearance are studied. But there would be no unity of experience, which is necessary for the unity of the subject and its objective orientation, if these appearances were isolated from each other, or related without any rule. If they were isolated, the subject would live in several worlds unconnected from each other without knowing how to move from one to the other, and consequently not knowing how to act in any of them. And if the appearances were randomly related, the subject could not be orientated in the experience, or there would be no cognition of what to expect, because it would not be possible to discern what happens, or what will happen, or what to do with each of these appearances. It is therefore necessary that they form a web, a network of connections and links, of regular successions and simultaneities, in other words, it is necessary for the subject, for its cognition and action, that the objects are not connected randomly but linked to each other by means of rules or concepts, thanks to which the subject can, firstly, place the appearances in the objective time and space and, secondly, establish their dependencies, their natural laws, with which to predict, dominate, use or avoid them, fend off them, etc. Judgment in the general formulation of the content of the three Analogies of Experience, as a condition of possibility of objective experience, arrives here at the basic and transcendental principle that: "Experience is possible only through the representation of a necessary connection of the perceptions" 44 .
However, Kant states in each of the three Analogies (although he still speaks only of time there) that in order to place the appearances in objective time and space, absolute time and space cannot be used, because these are not perceived 45 , as everything perceived must be limited, gone through and unified (synthesized) by the imagination. Therefore, the appearances can only be placed spatially and temporarily in relation to each other, i.e., "the appearances themselves must determine their positions in time [and in space] for each other […] in accordance with a general rule" (KrV A 200, B 245) 46 by means of their dynamic relation (with physical influences) and according to a universal rule. Hence the expressions that the sun is so many kilometres from Earth, or that the taking of the Bastille took place 1789 years after the birth of Christ, etc. This is also the case when their dependencies or causalities, as well as their simultaneity are determined, that is, in the three modes of time.
Hence, in the fifth place it can be said that the substance, as persistence, is necessary to be able to perceive and objectify changing appearances or alterations, and that both, what remains and what changes, are determined by each other, by contrasting the one with the other, because "all alteration presupposes something that persists in intuition, even in order merely to be perceived as alteration" 47 ; all consciousness requires distinction and contraposition. The persistent is the substratum of any change 48 and "that alone can represent the unit of time, namely the identity of the substratum in which alone all change has its thoroughgoing unity. This persistence is therefore nothing more than the way in which we represent the existence of things (in appearance)" 49 . Consequently, substance is an appearance, or object, or body that persists even though is it altered (verändert) 50 , while its accidents or determinations (Bestimmungen) change (wechseln) 51 and follow one another. This sensible persistence allows the positioning of the changing appearances in time and space, because it is not possible to resort to absolute time and space to proceed with that determination because they are not perceived.
The substance in Kant is not the essence of things (das Wesen der Dinge), but it is a moment of it. This essence of the appearance or realitas is expressed in the strictest manner by the categories of quality, their scheme and their principle. Alternatively, it could be thought that the essence of the appearance comprises the first three classes of categories, those of quantity, those of quality and those of relation, since modality does not contribute anything to the content of the object, but to its relationship with the transcendental subject 52 . However, the categories of modality can also be included, since they express the relation of the appearance with the transcendental subject and therefore also its character of appearance.

6.
Persistence is necessary to capture change. But why is change necessary? Kant does not explain this. Moreover, he believes that all alteration (Veränderung) is a posteriori, so that nothing could be said about it a priori 53 , "since alteration is a concept that can be drawn only from experience" 54 . Similarly, the possibility of movement (Beweglichkeit) of the substancematter in space is an empirical predicate 55 . Therefore, there would not be a transcendental necessity for change or alteration, or for accidents or movement, and the only thing that exists is the empirical finding that these occur empirically.
But if change is not transcendentally necessary, why should persistence be necessary, when they are correlative concepts, and having been accurately argued that persistence is necessary because without it change cannot be captured, that is to say, that the necessity for persistence has been made dependent on change? Change or alteration is required by the category of substance itself as the necessary opposing element, because if it is true that without the persistent it would not be possible to perceive change, the reverse is also true: without change it would not be possible to perceive what persists and lasts. The duration of the substance also implies the presence of changes, because "only through that which persists does existence in different parts of the temporal series acquire a magnitude, which one calls duration" 56 . This would not be noticeable without a sensible differentiation of successive moments of time by virtue of objective changes ruled by the law of causality.
It is my view that both permanence and change are transcendentally necessary as their contrast is required for consciousness and cognition. The need for persistence is expressed in terms of the category of substance whilst the need for change in terms of the category of accident, which in turn is also considered a category because categories of relation are necessarily dual. They do not synthesize homogeneous elements (Verbindung, conjuctio) that are sensibly given in the way categories of quantity and quality do, instead they combine different elements in their existence, that is, they are connections (Zusammensetzung, compositio) between two or more appearances and indicate "the synthesis of that which is manifold insofar as they necessarily belong to one another, as e.g., an accident belong to some substance, or the effect to the cause -thus also as represented as unhomogeneous but yet as combined a priori" 57 ,

RIVERA DE ROSALES, J.
and not purely empirically. The two categories, that of substance and that of accident, like all categories 58 , are original actions of the transcendental subject, which cannot be deduced from other, synthesize the phenomenal world in a regulated manner and point out transcendental necessities in view to order and interpret experience. Therefore, it is also necessary for change or alteration to occur together with persistence in the world of appearances 59 .
Kant affirms that time persists while appearances change over time, but as time in itself is not perceived, a visualization of that persistence by means of the phenomenal substance is necessary. He also states that fragments or moments of time are all successive 60 , and this succession of temporary moments could not be empirically captured if everything remained unchanged, but only if there are things that change from one moment of time to another. Therefore, there must be change in the appearances. That is the method of transcendental reflection: "everything in regard to objects of experience is necessary without which the experience of these objects itself would be impossible" 61 .
The first category of relation establishes that there must be persistence and change, but it is in the second category, the category of causality, where the category or law that governs and objectifies the change or temporal succession of the objects is determined: the effect cannot be prior to its cause, because the existence the former depends on the latter 62 . As a result, the categories of cause and effect require that there should be change and alteration, since without them there would be no causality, nor the establishment of the objective succession of appearances, nor objective cognition of the world, nor consciousness and self-consciousness.
It can also be argued that, if according to the first two principles, the Axioms of Intuition and the Anticipations of Perception, the extent and reality of each appearance has to be limited in order to be intuited, it follows that appearances also have to be limited in time, they must appear and disappear, and that constitutes change.
If there was no change there would be no inner sense, because this consists of a temporary flow of representations 63 . But if there were no inner sense, then the external object would not be understood as external, there would be no consciousness of it as such due to lack of distinction and contrast, the inner life of the spirit would be stopped, frozen, petrified, and with it the world and the transcendental I self.
Finally, if "all interest is, after all, practical" 64 and freedom "is the cornerstone of the entire construction of a system of pure, even speculative reason" 65 , as Kant explains in the Critique of Practical Reason, then it can be affirmed the transcendental need for change and movement in order to allow the realization of freedom and its aims in the world. Without changes there would be neither free action capable of modifying the world according to free purposes nor freedom itself, because freedom is not a transcendent substance that could be without a world, but it is an action of transformation of the world. There would therefore be no moral, no consciousness, and no subject. Nature cannot have an influence on freedom, but freedom must influence nature to fulfil its aims within it 66 and therefore it must be possible to modify it.
Hence, and that is the sixth idea, there must be change and, consequently, persistence cannot occupy everything, it must not be absolute: without change there would be no consciousness nor freedom. The phenomenal substance is also necessarily finite and modifiable.

7.
Persistence is not absolute, but change cannot be absolute either. If there were an absolute change, if suddenly everything changed radically with nothing persistent, that is, leaving no continuity, there would be a lapse in the world of experience, and its unity would be totally broken: the unity of time, of space and of causality, and with it also the unity of consciousness. Assuming the subject could survive, it would mean crossing from one world to another without a bridge or transition, magically, without any orientation or identity of the consciousness or continuity of the empirical self, for there would be an empty moment where there would be no experience 67 . "The general principle of all three analogies [of experience] rests on the necessary unity of apperception [or "I think" or transcendental subject] with regard to all possible empirical consciousness (of perception) at every time" 68 . There could not be an awareness of that absolute change, "for it is this very thing that persists that makes possible the representation of the transition from one state to another, and from non-being into being" 69 .
Thus, the seventh conclusion, there must always be something real that persists in timespace 70 without which there would be no experience nor transcendental subject, and that is the actual requirement expressed in the category of substance and in the first of the Analogies of the Experience. Here, the terms "always" and that "persist" are added to the Real (Realität) or qualitative realitas, that is, to what is presented as real in the category of quality and the Anticipations of Perception, which already points out that the material is the Real that occupies different spaces 71 . In the category of substance it is added that there must always be some phenomenal spatial and temporary realitas with a certain persistence or duration 72 .

8.
The transcendental requirement expressed in the category of substance is that something always persists or lasts in the experience, that not everything changes, in the same way that the category of accident states that always something changes and that not everything remains the same. But then, according to the first two principles (Axioms of Intuition and Anticipations of Perception), a body does not always persist due to its spatial-temporal-real, quantitative and qualitative finitude, or to their relationship with the other objects that can destroy it (causality and interaction).
Moreover, to our previous discussion that neither persistence nor change can be absolute, it can now be added that one body cannot persist absolutely. In the appearances nothing is absolute, because every object is finite in its quantity and quality, as it is in its interrelation with others. Everything that persists does not do so in relation to absolute time or space, since it cannot be perceived, but only by means of the interaction of some appearances with others, which can determine their modes of time: permanence, succession, simultaneity. The category of substance requires an appearance to be considered persistent in relation to others; the process of objectification considers that objects change and persist relatively to other appearances, in other words, that they remain in a mutual relation of some appearances with others, in such a way that whatever changes more slowly, or much more slowly, can serve as a permanent object, that is, as the substance for the perception and determination of others, and vice versa. In Plato's view, bodies do not comply perfectly with the requirements of ideas, as they do not comply in this context either with the transcendental demands expressed in the concept or category, which is universal and abstract because they express the rule as a rule, although bodies do so with respect to the demands expressed in the transcendental imagination, which works with the concrete.
Therefore, if the substance can only be altered (verändert) in its accidents but cannot be made to appear and disappear (wechseln) 73 , if the substance cannot arise nor perish 74 , it may be thought that, ultimately, the transcendental and ideal requirement expressed in the category of substance points not to something permanent that may be different in each case, but to something concrete and real always persistent in the time-space of the sensible world as the ultimate support of any change. That is the matter which Kant came to call "transcendental matter" 75 , along the lines of the Aristotelian-scholastic materia prima or first matter but regarded as an objective transcendental demand. In that case there would be only one substance and all the appearances of the world would be its various states or accidents. From the persistence of the substance, judged this time with the implacable universality of the concept, in an absolute way (not by simple analogy and with the "more or less" of the imagination that has to deal with the concrete and finite), stems the strict conservation of its quantity. From that perspective it could be said that matter is neither created nor destroyed, it is only transformed, as the chemical law of the conservation of matter of Lomonósov-Lavoisier says, and that is what Kant ultimately thinks in relation to the substance 76 . It then appears that there could be only one substance in the background, since all the objects in the world do appear and disappear, increase and decrease, and last or persist relatively.
Eighth idea: the phenomenal substance can ultimately point to the universal matter of all material objects, which would undergo alterations in time-space and should be the last substratum of everything that exists and changes in it. Relatively speaking, that is, given the relation of some appearances with others, there are many substances, that is to say, many objects in the sensible world that can be considered, and are in fact considered, as substances and also as persistent in relation to others; for example, this table is considered as a substance in relation to its colour, its parts, its defects, its place, etc. From that perspective there is a plurality of substances, and it makes sense to speak about them in this way and thus to apply the category of substance to give appearances an order. But it could also be affirmed that, in the final analysis, what the requirement of persistence, as expressed in the category of substance, points out to relates to the unique and universal matter from which all things in the world are made, which would be variations of that matter, resulting in a single substance.
Both uses or levels in the use of the concept of substance are accepted by Kant, because "matter is divisible indefinitely and specifically into parts that are equally matter" 77 , so that objects are also matter that move in time-space with its properties or accidents: "The concept of substance signifies the ultimate subject of existence, i.e. everything that doesn't exist merely as a predicate [here = 'property'] of some other existing thing. Now, matter is the subject of everything existent in space; for besides matter no other spatial subject can be thought of except space itself […]. So, matter-as what is movable in space-is substance in space. Similarly, every part of a portion of matter will also be called substance, and therefore also matter, insofar as (so fern) it can be said that they are subjects and not mere predicates of other matters. And they are subjects if they are movable and therefore also something existing in space outside the relation with other parts that were next to it" 78 , that is to say, insofar that they can move as an independent unity in space. In the "so fern" ("insofar as") one can see how the category of substance is a transcendental strategy to objectify and give order to the appearances, and not an ontic law of things as such 79 .
However, this transcendental matter has been thought of as such only from the universality of the category and from the concept of persistence as a concept, without taking into account the necessary concrete action of the imagination 80 and its empirical spatialtemporal limitations which we see, for instance, when Kant analyses the aesthetic sublime 81 . Although it can be understood that Kant affirms that the necessity for persistence expressed in the category of substance "is inseparably connected with the necessity to always having existed" (KrV A 185, B 229), i.e., with the existence of an identical substratum that always persists the same and thanks to which the unity of the objective time could be represented 82 , due precisely to that limitlessness in which the said transcendental matter is thought, this substance cannot become a phenomenal object, it does not actually become a sensible appearance, no more than unlimited time and space as such do, nor therefore does it make perceptible and secure the unity of time of all objects, that is, that they all share the same objective time 83 . This matter becomes sensible in the form of concrete objects, only they are perceived, and therefore only from them and their relations to each other, determined by the three categories of relation, their schemes and their principles (the Analogies of experience), can the modes of time and their unity in the experience be objectively determined 84 . Consequently, the most appropriate use of what is expressed in the category of substance is to refer it to the multiple sensible objects 85 . This is what happens in the third Analogy of experience, which studies the simultaneity of the various phenomenal substances or external objects that indicate each other's place and time through their interaction: "All substances, insofar as they can be perceived in space as simultaneous, are in thoroughgoing interaction" 86 . Here Kant talk about "a manifold of substances as appearances" 87 ; these are relative substances, that is, relatively to other appearances that change more rapidly, and that is characteristic of the phenomenal sphere 88 .
It is my opinion that it is not transcendentally necessary for a substance to always persist absolutely, as that is not sensibly noticeable, instead, only something sensible that persists is transcendentally necessary so that there is no interruption and discontinuity in the experience that results in empty time and space. But that does not prevent science from operating with the regulatory idea that all material is nothing but modifications of the same matter or energy in different variations, clusters, compositions, complexities, etc.; science continues on the path of discovering new and increasingly smaller particles of matter-energy in the direction of that absolutely persistent substratum or ultimate matter, providing that makes sense in something that is in continuous process 89 . Everything that bears the mark of the "absolute", in this case an absolutely persistent unique matter, surpasses the imagination and is outside the scope of understanding and Judgement, it is in fact an idea or a requirement of reason that does not have a constitutive, but at best a regulatory, function for objectivity.

9.
Yet, here we are referring to phenomenal matter, the matter that is found in time and space of objects. But in time and space there is nothing simple, no absolutely indivisible point, nothing that cannot be seen as compound. Therefore, in principle, everything that belongs to intuition as a sensible element of cognition "contains nothing but mere relation, of places in one intuition (extension), of alteration of places (motion), and laws in accordance with which this alteration is determined (moving forces)" 90 . Matter is exteriority and manifold, partes extra partes, it lacks simple parts (second Antinomy) that could always remain invariable, and neither does it configure a concrete totality or an unmodifiable and indestructible body, but it is also in principle unlimitedly divisible 91 . Hence, Kant affirmed when arguing against Leibniz and his concept of monad as a simple substance that "the inner determinations of a substantia phaenomenon in space are nothing but relations, and it is itself entirely a sum total of mere relations" 92 . Matter cannot contain anything internal, everything referred to as "internal" is meant to be comparatively so 93 . In the matter of the appearance there is nothing unconditioned. For that reason it can take multiple different forms and be configured in unlimited ways, which could not happen with indivisible elements that would always be equal to themselves, nor with unmodifiable and eternal bodies or totalities.
The subject demands that the phenomenal world should be modifiable to introduce into it its own conscious and free actions, but at the same time this world should be governed by laws, because only then the subject manages to cognize it, to orient itself and know how to act on it to achieve it aims, and that is precisely what is expressed in the categories of relation. But concrete, empirical laws have to be discovered, because the categories of relation are discursive and regulatory, not intuitive: they no longer provide the intuition of the other appearance connected with the one that faces us (contrary to what happens with the two first types of categories, quantity and quality, and with the application of their schemes), since the existence (of the other appearance) can never be deduced a priori, but it can only be indicated what has to be found, namely, the other element not yet sensibly given but necessarily connected with that given by intuition, for example the cause of an appearance, or what persists in it, or what other objects it interacts with and how, in order to recognise it when we find it, all by means of analogies with other cases 94 .
These concrete laws of the world can be varied and diverse. Even though Kant thought that Newton had laid the foundations for all of them, since the beginning of the 20 th century physics, chemistry and biology have been opening increasingly strange worlds, with appearances that surprise and challenge our imagination and understanding, accustomed as we are to move in our reduced conscious mesocosm. Given this diversity, human compression will always tend and try to bring all this manifold of appearances and laws to a system that should be comprehensive, and connected or coherent, appropriate to our capacity of cognition and necessary for the unity of experience through teleology, as a transcendental regulatory principle for understanding nature, as explained by Kant in his Critique of Judgement. The further we move away from the mesocosm, the more bizarre the world becomes. But we must always look for laws. For example, particle physics is determined to unify the four fundamental forces or interactions: the strong, the weak, the electromagnetic and the gravitational.
Ninth point: the phenomenal substance or matter is not something fixed, simple or indivisible, instead it is relational and, in principle, limitlessly modifiable, even though it is transcendentally required that it can be modified according to rules or laws, not arbitrarily or chaotically, since the latter would make objectivity and subjectivity impossible. Thus, subjectivity occurs, and there is ground to state that the world is the way we cognize it, at least to a sufficient extent.

10.
Although phenomenal substances and matter contain mere relations and nothing absolutely internal, they are nevertheless real and "the primary substratum of all outer perception" 95 and not mere idealities or pure illusion (Schein), but appearances (Erscheinungen).
Firstly, it is not a deception when we apply the category of substance to physical bodies, since they persist sufficiently in relation to other appearances and to our perceptions and the empirical speed of our life time, so that it is useful to consider them persistent and to identify them as singular objects with the view to ordering other appearances and themselves and to orient ourselves in the objective world. They are substances relatively. We say: "this tree is a substance", which is the same as affirming "this tree is an object" and we treat it as such, not because it always remains exactly the same, because it is born and dies and is in continuous movement or change, but because it does retain its unity for a while and responds sufficiently to that transcendental requirement compared to other appearances, for example, its growth or its change of colour and leaves in autumn or the nutrients it takes from the earth.
Secondly, and above all, the application of the concept of substance to physical bodies (or even to matter as the last substantial support of the phenomenal world) is justified because they present their own reality in the sense that they are not created ex nihilo by the subject, but they are given to it 96 , which justifies empirical realism, that is, that these substances are not mere idealities. This is recorded in transcendental Aesthetics, also in the qualitative category of reality (Realität), its scheme and its principle, a category to which the substance adds the requirement of persistence and of always. The phenomenal substance is not mere relation as if it were only ideality, but it consists of real relations and exhibits its own realitas, which is recognized in the category of reality, its scheme and its principle. Faced with these realities of the appearances, the subject behaves passively, they are given to it and it does not create them, which demonstrates that the appearances exhibit a certain reality from themselves, something that Kant tries to analyse using the problematic concepts of thing in itself and of sensible affection 97 .
Kant understands this mode of being and presenting itself that have the material objects, which makes the empirical realism of the substance possible, by means of the concept of force.
The phenomenal substance manifests itself to us as a force from itself capable of being a cause. "Causality leads to the concept of action, this to the concept of force, and thereby to the concept of substance" 98 . The action (Handlung) is an empirical criterion sufficient for substantiality, since it is only what persists that can cause that something else changes 99 . "Where there is action, consequently activity and force, there is also substance, and in this only must be the seat of this fruitful source of appearances be sought" 100 . Substance is the cause, because the effect is related to what changes, and what changes cannot be the cause of the change but the effect of what persists. "The category of substance lies at the ground of all concepts of real things" 101 .
Kant defends in his Metaphysical Foundations of Natural Science a dynamic conception of matter in line with the Leibnizian tradition, because according to him matter is made of two original moving forces, not deductible from others nor, of course, created by the subject, and it is because of these forces that matter fills a space. One is the expansive or repulsive force, also called elasticity, and the second is the force of attraction, which limits the expansive force and keeps the body within spatial limits. These physical forces and their occupation of time and space give empirical realism to the unity of the imaginative synthesis with which we interpret an object and its unity. "We know substance in space only through forces that are efficacious in it, whether in drawing others to it (attraction) or in preventing penetration of it (repulsion and impenetrability)" 102 . In that sense we have to see a plurality of phenomenal substances as forces that are in interaction according to the principle of action and reaction (Newton's third law).
Tenth and last point: the phenomenal substance and matter are dynamic, they are forces, about which it would be said nowadays, are ultimately energy. Matter-force or energy is the origin and the real cause of all appearances, both of them being considered as substance and their accidents. In addition, since matter-force does not contain simple elements 103 , as previously stated, phenomenal substance is formed by a field of forces, with no simple elements. This is the final conclusion, not very different from modern physics and its field concepts 104 .

notaS / noteS
1 Jacinto Rivera de Rosales is Professor of Philosophy at the UNED (National University of Distance Education), where he teaches History of Modern Philosophy. He has specialized in German Classical Philosophy, about which he has published numerous articles and also books such as El punto de partida de la metafísica transcendental. Un estudio crítico de la obra kantiana (Ediciones Xorki, Madrid, 2011) or Fichte (RBA, Barcelona, 2017) also translated into Italian and French. He has been President of the International Fichtean Society (IFG, 2012-2018) and of the Society of Kantian Studies in Spanish Language (SEKLE, 2014(SEKLE, -2018, and is Coordinator of the Iberian Network of Fichtean Studies. He is organizing a conference on Schelling, and belongs to a research group on Hegel, another international on Hermeneutics and a third on contemporary Nihilism.