Kurt Riezler was Kurator (regent) and professor of philosophy at the University of Frankfurt from 1928 to 1933, where he assembled an outstanding faculty including Max Horkheimer, Theodor Adorno, Max Wertheimer, Herbert Marcuse, Karl Mannheim, Paul Tillich and others. Riezler attempted to recruit Heidegger as well and although he did not succeed, the two became good enough friends that Heidegger stayed with Riezler when he visited Frankfurt.

As seen in his 1940 Physics and Reality lectures, given in New York after Riezler’s emigration from Germany, he was greatly influenced by Heidegger’s appeal to a renewed consideration of Being and to do so especially with Aristotle. Indeed, in these lectures, Riezler spoke in the name of Aristotle.  First person constructions in the selections below therefore relate to the Stagirite, while second person constructions refer to contemporary physicists.

The nature you talk about as scientists is not the nature you mean when you say ‘l am’. Nature is one, immutable,  eternally varying — the way of Being in all beings, revealed as eternal movement, formation, deformation, and transformation. You yourselves, [with] your desire for knowledge, you are Nature. And yet you have opened between your comprehension of yourselves and your knowledge of Nature a chasm that engulfs in darkness your common being.  

You cannot (…) find the way back to the unity of Being, to that one Nature in which you are kin to all beings, the eternally equal, which, imperturbable, conceals and reveals itself in all that is. 

You dispense with ‘is’.

A statistical law does not state anything about the nature of elementary events. It is from their inherent nature, preliminary to all aggregates, that the arrow of Time springs. Here must be its source. This source you cannot find.

The answer the world gives to your way of questioning is an order of [instrumental] pointer readings. (…) This answer is an answer neither of the world nor of your own Being. You can make it pass neither as one nor the other. You have not examined the ‘Being’ of the subject. Maybe from its knowledge of its own Being the subject would have given [and been given] an entirely different answer. [But] you have lost the ability to inquire in that way: you no longer even know that such a way of inquiry is possible and still less that you could obtain an objective answer to such questions. 

You know and accomplish a great deal, yet you have no picture of Nature, no total design of Being. 

You have cut science into parts. I am aghast, seeing that in your hands the specialization of sciences has resulted in dissecting the world into many worlds. I cannot make myself believe that this satisfies you. The world is one. Nature is one. One tie links all Being. That uniting logos of Being must be unearthed. My name for this task, ontology, has acquired ill fame. But what’s in a name? The task remains — soluble or not — yours [today] as [much as] it was mine [yesterday].

Thought, even when proceeding  without contradiction, remains empty unless it refers to Being. We must question Reality and listen patiently to what it condescends to tell us.

The logos of Being revealed in you and in the world surrounding you — that is the kind of knowledge Man by his very nature longs for.

In putting this question you must step back¹ — far, perhaps so far as to revise the meaning of the’ is’ in your questions. 

I must go behind your very first assumptions. I return to the meaning of the tiny word ‘is’.

There is in your subjectivity an objective reality by virtue of which you ‘are’. That is what I am speaking of. It is the soil all beings are rooted in.

I court Being in this sense. On this quest you must not start from an order of the Many in space and time. 

The inward denseness, not the outward breadth, has to be grasped. What l am searching for I call ‘Being’, concreteness, [the] Being of beings so far as they ‘are’

Empty is this cosmos and all within it futile unless it is founded in this Being of Being. 

Only the whole ‘is’. In this whole the inner density of Being resides. 

My master and friend, Plato, said: all Nature is ‘born together’ [Menon 81d]. This statement, interpreted as a statement about the order of the cosmos, would mean: all the different beings that exist — stones, animals, plants, stars — were born together.² That is not the primary sense of Plato’s words. Not the Many, distributed in time and space, were born together, but that logos by virtue of which every one of these Many has its being is a unity of ‘momenta’ that are born together.³ The body of this unity cannot be disjointed. Physis means the nature of Being qua Being. This nature is the same in all beings that ‘are’.

It is not the Many of the world ordered in space and time, but the oneness of Being folded within itself. It is this One that needs to be inquired into and comprehended before the Many can be brought into an order.

You must seek in a quite unaccustomed way. Nature is one. The little word ‘is’ [here] has a double meaning. Corresponding to this double meaning are two senses of the word ‘nature’. First yours: the order of the Many in time and space, Nature as world. Then mine: nature as  ‘Physis‘, the structure of concreteness so far as the concrete is concrete; Nature as Being.

Nature as world is ‘given’ as a compound of phenomena in the breadth of space and in the length of time. Nature as Physis is revealed to you in yourselves as [the] inner density of your existing, as [the] substantiality of your Being. Either is [= ‘can be’] experience. To each kind of experience corresponds a way of putting questions: To the first, the question concerning the order of the Many, the frame of this order, the relations connecting the Many, the laws governing these relations. To the second corresponds another way of questioning: inquiry into ‘Being as far as it is’, into that logos and that community of momenta in which reality is really real. To me the second question is the one to be put first. You lost sight of this question when you separated subject and object. Thus the double meaning of ‘is’ cleaves in two the meaning of the word ‘nature’, of experience, the framing of the question, the logos of an answer, and [of all] knowledge. And yet Nature is one in both senses of ‘is’, in both kinds of revelation, in both ways of putting questions. This unity is Nature’s own secret. To distinguish the two senses is not a whimsy of human thought and speech; the realness of reality imposes it. A Mystery divides and unites the two. It will not do to put the one question without also putting the other.

Being is nothing without a world in which it is actualized, vain is a world that does not reveal Being. Either reading of Nature remains devoid of meaning without the other. Only in each other ‘are’ they both. 

Being is a logical unity, the unity of a structure. (…) Each [particular one] is a One, however, not only by virtue of being countable as one but by that very unity of modes united in a logos whose wholeness is antecedent to its articulations.

Nature antecedes your separating subject and object. She embraces both. Their correlation is what is ‘given’ first. If you separate the two and break their unity she will elude you.

You receive reality from others as well as give it to others. In give and take, in to and fro, in the concord and discord of both, has your Being the wholeness of Being.

In between all these momenta, in their unity, tension, conflict, Substance ‘is’ and confers Being on things through relating them to itself. 

The order of the Many, called ‘world’, is a plurality of Ones. These Ones are Ones by nature not by human thought. They are autonomous Ones, substances. In Substance the substantiality of the One and of the Many is tethered. Substance unites World and Being. Through Substance World becomes Being, Being becomes World. All other categories are related to Substance. Like Substance they must (…) play a double role: they must order the Many and articulate the logos of Being. Charged with erecting the frame of the order of the Many, these categories should have a meaning in that logos of Being qua Being that is able to cover the inner concreteness [of all things]. 

Being includes the correlation between Subject and Object that is antecedent to your separating. 

I inquire into ‘Being’ — into the structure of the logos by virtue of which a being essentially ‘is’. 

Consider the kind of Being you must attribute to your language, when you are not actually speaking it. It exists in that mode of Being I call possibility. The essence of language is that it can be spoken. But language is not a mere sum of possible utterances, of vocabulary, and grammar. It is an organized whole, a system, embracing an immensity of possible phrases, styles, manners of good and bad speaking. This mode of Being, I confess, is not altogether easy to grasp. In its innermost life language seems to be animated and governed by something you call its spirit: a thing to be neither denied nor understood clearly. (…) You may think and speak of the different styles of a language as of spaces in space, fields in a field. (…) In this general apace, which is neither your space nor your matter, you and the others to you are begotten. The different individual fields are not side by side, unconnected. They are in a more general field. It is in this field that you actualize yourselves as individual fields, and so do the others. Thus your moving changes the fields of the others [and] their moving changes yours.

All these momenta of time, however, are ‘born together’; none can be isolated. Thus in articulating Substance we articulate Motion; in articulating Motion we articulate Time; but in all this articulating we meet one and the same logos of momenta, interconnected by an eternal necessity: the logos of Being. Nature’s very nature.

The logos of substance uniting the creator and the creature,  natura naturans and natura naturata, is the logos of Being — to be enjoyed and to be endured.

Relation is prior to the relata. You actually do not define one by means of the other but each by means of a whole that is articulated within itself.

The One is folded within itself.

Being is immortal; all beings die.

Reality has both an outward breadth and an inward density.⁴ (…) The two are correlated. They must be seen together. The one must help you to decipher the other. Their relation  precedes the relata.

So you [must learn to] know Being — the realness of reality. Try to grasp the iron logos welding together the inseparable joints of this Being; you will find it at the bottom of whatever you choose to look into.