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Section 3: The Ontological Priority of the Question of Being (pp.28-31)

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In sections 3 and 4, H argues that there are two keys ways in which the Seinsfrage is of utmost philosophical importance. In other words, he argues that in two key ways, answering the Seinsfrage is a requirement for answering many other philosophical questions. Here in section 3, he argues for the question’s ontological priority, which concerns the nature of scientific inquiry; whereas in section 4 he argues for its ontical priority, which concerns human nature.

We should first note that “ontological” and “ontical” are two central Heideggerian terms. “Ontological” means ‘concerning being’, and “ontical” means ‘concerning entities (beings)’. The distinction between ontological matters and ontical ones is grounded in what H calls the ontological difference: the idea that there’s a fundamental difference between being and entities. H thinks, roughly, that being must be distinct from entities because it’s that which determines entities as entities.1 Now, remember that to answer the Seinsfrage, H thinks we must interrogate entities, and for two reasons. First, being, as he reminds us here, is always the being of entities. That is, what ties together the different senses of being is that they all apply to entities, so it is to this common factor – entities – that we must turn to understand being. Second, though, we must interrogate a particular entity in particular: Dasein. However, it’s important to remember that neither of these is the case because any entity, including Dasein, is what we’re asking about in the Seinsfrage. Rather, as we learned from section 1, the first is the case because the various senses of being all apply to entities; and, as we learned from section 2, the second is the case because to understand clearly what we’re asking when we pose the Seinsfrage, we need to get clear on our being as sense-making creatures.

Given all that, in what sense, then, does the Seinsfrage have ontological priority?

H’s aim, as we know, is to understand the being of entities as such. However, he also thinks it’s possible to inquire into the being of some particular sub-class ofentities: what he here calls a domain (and elsewhere calls a region) of being. Because the latter sort of inquiry concerns being, let’s call it regional ontology. To distinguish regional ontology from the more general sort of inquiry that he wants to undertake (which so far we’ve just been calling ontology), H will sometimes call the latter fundamental ontology. H’s main claim in section 3, then, is that fundamental ontology has a certain kind of priority over regional ontology: namely, in order to have a satisfactory understanding of the being of those entities in a certain domain (i.e. a satisfactory regional ontology), we must have a satisfactory understanding of the being of entities as such. If he can convincingly argue for this, it will help H to convince many of his readers that fundamental ontology is of utmost philosophical importance – namely, those who think that questions about regional ontology are of vital importance for understanding the nature of scientific inquiry.

To understand section 3’s main claim, then, we first have to clarify the notion of a regional ontology, and its role in scientific inquiry. Here in section 3, H considers forms of systematic inquiry (i.e. sciences, in a broad sense of the term) like mathematics, biology, history, and theology. Any science has its subject matter—the domain or region that it studies. For example, the domain of biology is that of living things, and the domain of history is that of historical phenomena. Given this, H thinks that in order to practice any science – to inquire into its domain in a systematic way – normally you must presuppose some regional ontology: i.e. some understanding of the being of entities in that domain. This understanding, H alternatively puts it, is made up of the basic concepts of the science.

Recall from my comments on section 2 that the being of an entity is what determines the ways in which the various senses of being are applicable to it. For example, it determines the various claims about what things (there) are that are true of it. In other words, it determines (a) what properties it must or could have, as well as what properties it would have in various circumstances; (b) its identity (i.e. which entity it is); and (c) what’s required for it to exist. So, when H claims that practicing a science normally presupposes some regional ontology, he means that it normally presupposes some understanding of (a)-(c), as they pertain to the entities in that science’s domain. Specifically, such understanding is normally presupposed in the sense that it’s normally never called into question, but operates in the background in such a way that accepting it makes it possible for us to undertake particular investigations in that science.

This is rather abstract. So, to clarify things, let’s consider one of H’s own examples in more detail: mathematics—specifically, number theory (i.e. the mathematics of numbers). To use H’s terminology, numbers make up the domain or region of number theory. In what sense, then, does the practice of number theory normally presupposes an understanding of (a)-(c) as they pertain to numbers? Let’s consider each in turn.

(a) Properties

As mathematicians practice number theory, they presuppose, in the above sense, many things about the properties of numbers. Consider the simplest examples of numbers: the natural numbers (0, 1, 2, 3, etc.). In the historical past, mathematicians have presupposed, first, ideas about the properties that numbers must (i.e. necessarily) have. They’ve presupposed, for instance, things like that 2 is necessarily an even number; or that each number is necessarily greater than the previous number in the natural number series (e.g. that 2 is greater than 1, that 3 is greater than 2, etc.) Second, mathematicians have presupposed ideas about the kinds of properties numbers could have. For instance, they’ve presupposed that numbers can’t have many kinds of properties that physical entities can have: e.g. that a number doesn’t have a weight, a height, a spatial location, a color, a speed, and so on. Lastly, mathematicians have presupposed ideas about the properties that numbers would have in various circumstances. Such presuppositions are embodied, for example, in their practices of formulating, accepting, and rejecting mathematical proofs. Suppose, for example, that a mathematician formulates, and that the greater community of mathematicians accepts, a proof that all even natural numbers have property F. And, imagine that, in the proof, this conclusion is drawn from premises X, Y, and Z about the even natural numbers. Accepting the proof, then, presupposes that the even natural numbers would have F in the circumstances where X, Y, and Z are true. This speaks to something more general: embodied in the shared sense that the community of mathematicians has of what makes for a successful proof is a systematic sense for which properties numbers will have in which circumstances, so that if one can show that certain circumstances obtain, one has thereby shown that certain numbers have certain properties.

(b) Identity

As mathematicians practice number theory, they normally presuppose many things about the identities of numbers. For example, historically they’ve presupposed that each member of the natural number series is distinct from all the others: e.g. that 1 is distinct from 2, 3, 4, etc. Or, they’ve presupposed that if numbers x and y are both successors of number z, x must be one and the same as y. For example, if x and y are both successors of 3, x and y have to be one and the same number: namely, 4.

(c) Existence

Historically, mathematicians have been very interested in figuring out what kinds of numbers there are—i.e. what kinds of numbers exist. Thus, at various points in history, they’ve figured out that there are numbers less than o (i.e. negative numbers), numbers in between the integers (i.e. non-integer real numbers), numbers that are the square roots of negative numbers (i.e. imaginary numbers), etc. The way that they’ve figured such things out has been, again, by way of mathematical proofs. Here, then, we can make a point parallel to the one made above. That is, the shared sense that the mathematical community has of what makes for a successful proof of the existence of a certain kind of number constitutes a sense for what’s required in order for that kind of number to exist.


Let’s try to bring all of this together. H’s idea would be that these kinds of presuppositions together make up an understanding of the being of numbers—a regional ontology for number theory. Normally, these presuppositions aren’t called into question, but operate in the background. For example, for many centuries it probably would never have occurred to number theorists to question whether 2 is an even number, whether it’s distinct from 1, or whether it exists at all.

But remember also that, on H’s picture, this kind of regional ontology normally makes it possible for mathematicians to participate in the practice of number theory. Why does he think this? Why, in other words, would it be impossible for us to practice number theory if we didn’t do so in accordance with such presuppositions?2

Imagine a person A comes to us and says she’s going to investigate the number 5. A is a mathematician, and we’re used to her telling us about her latest projects. However, when she continues, A says: “What I want to do is to to figure out where the number 5 is. Currently, I’m considering two major hypotheses: first, that it’s in my car; second, that it’s somewhere in my sister’s garage.” How would we react? Whatever we think A’s up to, we couldn’t, you might think, conclude that she’s doing number theory. To be doing the mathematics of numbers, you have to simply presuppose certain things—for example, that numbers aren’t the sorts of entities that have spatial locations. If A isn’t doing number theory, then, what could she be doing? Well, perhaps she’s making a strange sort of joke. Or, perhaps she’s using the phrase “the number 5” differently from how we thought, and we’ve just misunderstood her. For example, it could be that she’s using the phrase as a shorthand for “the model number 5 screwdriver I own”. In this case, she’d be undertaking a perfectly intelligible investigation: she’d be looking for her screwdriver. However, this wouldn’t be a mathematical investigation, let alone one in number theory. Or, perhaps A has become dramatically confused about what numbers are: e.g. gone mad, or fallen under the influence of some strong hallucinogen. In this case, though, again it seems that she’s so far off the mark in her understanding of numbers that she can’t be said to be practicing the science of them at all. To use an analogy to the game of chess: A’s less like someone who accidentally moves the rook diagonally, and more like someone who starts swallowing the pieces one by one. The former sort of person is still playing chess, but has made a mistake in the game. The latter sort of person, though, is so far off the mark that they’re no longer playing chess at all. Similarly, A has gone off the rails so badly that it would seem she’s no longer doing number theory at all.

The background idea here is that in order to engage in a certain science at all, you normally have to just presuppose certain things about the entities in the domain of that science. In the example I just described, I imagined A failing to make a key presupposition about numbers of type (a). However, we can imagine other examples of type (b) and (c). If, for example, A had told us that she wants to show that the number 5 and the number 24 are simply one and the same number, or that the number 5 doesn’t exist, our reactions would likely be similar: whatever it is she’s doing, it’s not the mathematics of numbers, because in order to practice that science at all, you simply have to accept the presuppositions that A would thereby reject. We can see, then, why H thinks of these presuppositions as constituting an understanding of the being of the entities in the relevant science’s domain. In the above case, they make up an understanding of numbers that tells us about the ways in which the various senses of being (specifically, in claims about what things (there) are) are applicable to them. Again, we can speak of this understanding as made up, as H also puts it, of the basic concepts of number theory.

With this clarification of the notion of a regional ontology under our belts, let’s return to the main claim of section 3. Again, this is the claim that in order to have a satisfactory regional ontology, we must have a satisfactory understanding of being of entities as such—i.e. an answer to the Seinsfrage. How does H argue for this?

One key thing to notice about how I was speaking above is that I talked about how a science normally operates. But, H tells us, “[t]he real ‘movement’ of the sciences takes place when their basic concepts undergo a more or less radical revision which is transparent to itself” (p.29).3 In other words, H has in mind cases where a science reaches a point at which it cannot move forward with the regional ontology that has, up to that point, made the practice of that science possible. Such historical upheavals in a science correspond roughly to what the philosopher of science Thomas Kuhn famously called paradigm shifts, or scientific revolutions.

A paradigm shift is a very dramatic kind of change in a science. It isn’t just a change in which scientists reject one view of some particular thing or kind of thing—a kind of change that happens all the time. Rather, it’s a change in which fundamental aspects of the science’s conception of its subject matter, methods, and aims undergo a radical alteration. One common example of a historical paradigm shift is the one that occurred in physics in the 17th century, from Aristotelian mechanics to classical mechanics. For instance, in Aristotelian mechanics, it was presupposed that physical changes have purposes, and that these purposes are essential for understanding the natures of those changes and the physical phenomena involved in them. This was presupposed, for example, in the shared sense that physicists had of what makes for a satisfactory explanation of a physical change, or of the natures of the phenomena involved in it. However, in classical mechanics, these presuppositions evaporated, and physicists thought of themselves as in the business of discovering exceptionless, necessary laws of cause and effect in which the concept of purpose plays no essential role.

H’s idea here in section 3 is that what changes in such scientific revolutions is a science’s regional ontology: the normally unquestioned presuppositions about the being of the entities in that science’s domain that make it possible for people to practice the science. In the present example, the notion that physical changes have purposes wasn’t a result of investigations of Aristotelian physicists—something that they thought they discovered, the way that modern scientists might someday discover that there are living microbes on Mars. Rather, it was a presupposition that was, for them, deep in the background, underwriting all of their methods for investigating physical phenomena, and arguing for particular views about them. It was, in other words, rather like the view that the number 5 is distinct from the number 24.

However, there are many examples of times when such background assumptions of a science have started to seem more and more untenable, or when the practitioners of the science start to wonder whether grounds can be found for them. The example of the 17th century revolution in physics is an example of the former. An example of the latter can be found in the celebrated foundational crisis in mathematics in the early 20th century. For example, at this time mathematicians and philosophers labored to understand why the natural number series has the structure it does—e.g. why we ought to accept the kinds of presuppositions we discussed above about the identities and relations of the natural numbers. In the course of their reflections, they formulated models of this structure that suggested the existence of so-called ‘non-standard numbers’ (numbers that aren’t members of the natural number sequence, as we usually conceive of it), and debated about why we ought to accept our ordinary conception rather than one of these non-standard models. Among the views they put forward are the ones that H mentions here in section 3: intuitionism and formalism.

In H’s terminology, these are times when the regional ontology of a science itself becomes a subject of debate. But this raises the question: how should we adjudicate debates like this? It’s particularly difficult to figure out how to do so. That is, if what’s being questioned are deep presuppositions of many or even most of the methods of a science, then it would seem questionable to use those methods to adjudicate such debates. But if we can’t use those methods, which methods should we use?

H’s suggestion is that, since what’s being questioned in such debates about a science is the being of the entities in that science’s domain, answering the Seinsfrage—i.e. understanding the being of entities as such—will help us understand what’s going on in such debates, and shed light on the proper ways of adjudicating them. In other words, if we can understand the being of entities in general, this will help us to understand how to settle questions about the being of some particular sub-class of entities. For this reason, H’s own project of answering the Seinsfrage ought to be of interest to any philosopher interested in the nature of scientific inquiry, and indeed to any scientist who’s faced with a crisis in their science’s foundations.


1. This motivation for the ontological difference is, it should be noted, incomplete. Crucially, for example, it overlooks the possibility that being is an entity, but special among entities in that among the entities it determines as entities is itself. Historically, many philosophers have embraced this possibility. For example, they have done so by identifying being with God: a view expresse by many medieval and early modern philosophers by saying that God is self-caused.

2. Seasoned readers will notice that in what follows, I’m relying on Ludwig Wittgenstein’s way of approaching a similar question in his On Certainty. I do so in the belief that there are enough similarities between Wittgenstein’s notion of a system of ‘hinge proposition’ and Edmund Husserl’s notion of a regional ontology (on which H is drawing in this section) to make Wittgenstein’s approach a useful way of illuminating the present aspects of the former notion.

3. All page numbers refer to the translation of Being and Time by John McQuarrie & Edward Robinson (New York: Harper & Row, 1962).