20th WCP: The Formality of Reality: Xavier Zubiri's Critique of Hume's Analysis of Causality

I. Introduction

Causality has been a pivotal concept in the history of philosophy since the time of the Ancient Greeks. After David Hume, however, many have questioned whether there is (or can be) any metaphysical meaning of causality, or valid inferences based upon it. Xavier Zubiri (1898-1983) has rethought and reformulated the question of causality in light of its historical roles, well-known criticisms, and relevant contemporary knowledge. In doing so, he has achieved a unique perspective on the subject which should be of great interest to those concerned with causality and any of its applications.

II. Hume's critique of causality

The figure of David Hume looms large in the philosophical tradition of English-speaking countries; and his two famous analyses, of human apprehension and of causality, were the most penetrating up to his time, and continue to have great influence. As the culmination of British empiricism, Hume's work is especially important because he realized the importance of analyzing human apprehension both as a step in the development of a comprehensive philosophy, and in connection with the problem of causality. This task Hume undertook in his Treatise of Human Nature, Book I. In Part IV, he is concerned to establish a reason or explanation for our belief in the independent and continuing existence of external things or 'bodies', for upon this all causal reasoning about such things must ultimately rest. As is well known, Hume argues that such belief must either come from the senses, reason, or what he terms 'imagination'; and he dismisses the first two, leaving only the last, where he attributes the belief to coherence and constancy of impressions. (1)

For the present study, details of Hume's argument are not as important as his basic assumptions. One of those assumptions, never explicitly stated but always lurking just beneath the surface, is that all reasoning and understanding of the external world comes from the mind working on the content of sensible impressions, be they pains, pleasures, colors, or sounds. The burden of inferring the existence of things outside of the mind then must fall upon the mind and those processes available to it, because what the senses deliver is inadequate to the task:

That our senses offer not their impressions as the images of something distinct, or independent, and external, is evident; because they convey to us nothing but a single perception, and never give us the least intimation of anything beyond. (2)

This leads to Hume's analysis of causal relations:

....Thus we remember to have seen that species of object we call flame, and to have felt that species of sensation we call heat. We likewise call to mind their constant conjunction in all past instances. Without any further ceremony, we call the one cause, and the other effect, and infer the existence of the one from that of the other. (3)

A bit further on, Hume remarks, "...the relation of cause and effect is requisite to persuade us of any real existence ..." (4)

Given Hume's point of departure, and his fundamental assumptions about the nature of human apprehension, human intelligence, and reality, Zubiri believes that there is no escape from his skeptical conclusions. Accordingly, Zubiri does not criticize Hume's reasoning; rather, he analyzes the extremely deep-seated assumptions in Hume's philosophy, to show that they are at fault and responsible for his erroneous conclusions.

III. Brief summary of Zubiri's philosophy relevant to Hume's analysis

Zubiri long pondered the great philosophical questions, and as befits serious philosopher, he did not adopt a "motto"; but had he done so, it would undoubtedly have been his friend Einstein's keen observation: "The significant problems we face cannot be solved at the same level of thinking we were at when we created them". Accordingly, Zubiri believes that prior to development of any epistemology, such as Hume's, it is first necessary to go one level deeper in order to fully analyze human intelligence. This analysis is not a new theory, only a pure and rigorous description of that intelligence; but it is one which has been consistently overlooked or treated inadequately by earlier philosophers, including Hume. Only after it can construction of an epistemology commence and metaphysical reasoning begin.

For Zubiri, perception of reality begins with the sensing process; but in contrast to Hume and classical philosophy, Zubiri does not believe that there is duality of sensing and apprehension. What we have, rather, is a fully integrated process that immerses us in reality:

As impression is what formally constitutes sensing, and reality is what formally constitutes intellective knowing, it follows that saying that the moment of reality is "in" the impression is the same as saying that intellection is structurally "in" the sensing; i.e., the impression of reality is intellective sensing. For this reason, when we apprehend heat, for example, we are apprehending it as real heat. An animal apprehends heat only as a thermic response sign; this is pure sensing. In contrast, man senses heat as something "in its own right", as something de suyo: the heat is real heat. (5)

Direct apprehension of reality through sensible impression is a process which is intrinsic to our somatic structures as human beings. It is, indeed, the most important characteristic of our apprehension, and the foundation of all subsequent knowledge, including all rational knowledge. This impressive apprehension of reality is an act of what Zubiri terms the sentient intelligence (as opposed to earlier conceptions of it, which he refers to as sensible intelligence):

By virtue of its formal nature, intellection is apprehension of reality in and by itself. This intellection...is in a radical sense an apprehension of the real which has its own characteristics...Intellection is formally direct apprehension of the real—not via representations nor images. It is an immediate apprehension of the real, not founded in inferences, reasoning processes, or anything of that nature. It is a unitary apprehension. The unity of these three moments is what makes what is apprehended to be apprehended in and by itself. (6)

This fully integrated nature of the sensing and intellection aspects of perception implies that the Scholastic maxim nihil est in intellectus quod prius non fuerit in sensu nisi ipse intellectus is radically false. (7)

Zubiri divides human intelligence into three modes or phases which unfold logically if not chronologically as follows:

Primordial apprehension of reality (or basic, direct installation in reality, giving us pure and simple reality).
Logos (explanation of what something is vis à vis other things, or what the real of primordial apprehension is in reality).
Reason (or ratio, methodological explanation of what things are and why they are, as in done in science, for example).

Of these, primordial apprehension is the most important; it is the product of our somatic structures, and it puts us into direct contact with reality. Thus it comprises the foundation for all other knowledge. Zubiri's point of departure for describing primordial apprehension is the immediacy and sense of direct contact with reality that we experience in our perception of the world; the things we perceive: colors, sounds, sights, are real in an extremely fundamental sense that cannot be overridden by subsequent reasoning or analysis. That is, there is associated with perception an overwhelming impression of its veracity, a type of "guarantee" which accompanies it. Implied here two logically separate but operationally inseparable aspects of perception: first, what the apprehension is of, e.g. a tree or a piece of green paper, and second, its self-guaranteeing characteristic of reality. Zubiri terms these content and formality of reality, respectively. They form a tight unity, characterized by an intrinsic moment of otherness; and together they install us, however modestly, in reality.

The impressions given in primordial apprehension need to be sorted, understood, named, and related to other, usually prior impressions. For example, if a piece of green paper is apprehended in primordial apprehension, one has indeed apprehended green; but knowing that it is green requires knowledge of colors and a comparison of this newly apprehended color with known colors and their names from prior apprehensions. This mode of intellection, based on primordial apprehension, is an ulterior mode termed 'logos'. Thus knowing, in the logos stage of intellection, is primarily concerned with relating what a thing, apprehended as real in primordial intellection, is in relation to other things.

The third level of intellection, ratio or reason—with the broad acceptation of explanation—encompasses far more than what is usually associated with this word in English-speaking countries, viz. discursive knowledge. In particular, knowledge is not just science; there are other modes of knowledge, for example poetic knowledge and religious knowledge, which fall under the scope of reason as Zubiri understands it. Correlatively, there are realities which are not things in the sense of objects of science; for example, there is the reality of the person. In Zubiri's words, reason is "measurant intellection of the real in depth". (8)

IV. Zubiri's Critique of Hume

To return now to Hume and causality, Zubiri agrees that "causes", in some metaphysical sense, are not given in experience:

In classical philosophy a cause is that from which something proceeds by means of a real influence upon the being of the effect. Now, causality is not something given. We never perceive the productive influence of a real thing upon another....Our perception never perceives causality, but always does perceive the functionality; in the field of reality we sense reality in its functional moment as a field-nature moment of the impression of reality. We perceive that a thing is real as a function of others, and functionality can be and is quite varied. (9)

Zubiri believes that Hume's argument fails because his analysis of intelligence is wrong on two critical points: (1) our intelligence is sentient, not sensible; as a consequence, we perceive reality directly—we do not need causal inference to reach it. That is, the "impressions" we have are not sensory impressions but impressions of reality, which have two aspects, content and formality, as discussed above. (2) Hume's analysis of human intelligence into reasoning about impressions or "matters of fact" based on causality, and reasoning about "relations of ideas" which ultimately must refer to some impression, is radically false. The correct analysis must center on the far more complex and subtle three stages by which our knowledge unfolds: perception of reality, logos, and reason. Understanding of both of these points is necessary in order to unravel the problems of Hume's analysis.

Hume acknowledges that we have knowledge of the "external" world, which he thinks we base on raw sense data and causal inference, in turn identified with constant conjunction: "...any conclusion (about matters of fact) beyond the impressions of our senses can be founded only on the connection of cause and effect.". (10) There are two errors here. First, Hume has failed to distinguish the basic act of sentient intelligence—primordial apprehension—from subsequent acts—logos and reason—which involve the intelligence in more discursive ways. As a result, he has failed to recognized that the type and veracity of knowledge obtained in these acts differ sharply. Second, he has collapsed all types of discursive knowledge of the world, assuming that it all must be based on causality, identified with constant conjunction. Because there is a superficial plausibility to both of these errors, the overall argument achieves a significant degree of plausibility despite the fact that Hume himself admits that he cannot live his life as if its conclusions were true.

So what is really going on? First, that on which we base our knowledge, whether at the level of primordial apprehension or at the higher levels, is not constant conjunction. It is, rather, functionality, considered in a very general sense. Functional relations may or may not involve causality in the traditional, deterministic sense, or Hume's version, constant conjunction; functionality is a much broader concept, capable of supporting inferences such as counterfactual conditionals which are beyond the range of constant conjunction. Furthermore, functional relationships may be—and indeed often arestatistically based, for which constant conjunction as an explanation is hopelessly inadequate. Functional relations exist for all three levels of intelligence, beginning with primordial apprehension, which leads directly to the second point (and Hume's principal error).

At the level of primordial apprehension, Hume failed to distinguish content and formality of reality in impressions. Hume assumed that content was the locus of causality—and therefore of all of our knowledge of the external world (which, via functionality, it is at the higher levels). But in fact it is formality which delivers reality to us, at this most important level, that of primordial apprehension. Zubiri notes:

For Hume, causality is not given, but only temporal succession. Now, I have just said myself that causality is not given. But Hume did not notice that there are two different aspects of the question. First of all, he did not see that temporal succession is just a form of functionality. In the second place, the succession is not the succession of two impressions, but the same impression of reality, one which is of successive nature—which means that what is essential about functionality does not concern the content of the impressions but their formality of reality. (11)

In other words, an impression of successive events gives the functionality and the reality of the succession at the same time. Thus through formality, functionality does give us knowledge of reality, so that Hume's skepticism is misplaced. Zubiri would agree that if we had to rely solely upon reasoning which utilizes the content of impressions as the basis for our knowledge of reality, we could not escape Hume's conclusions. We do in fact rely on such reasoning for much of our knowledge, at the level of logos and reason; but all such knowledge would be impossible if reality were not first delivered to us in primordial apprehension.

This can be best understood through Hume's own example of the ringing of a bell when its cord is pulled:

In Hume's example, the ringing of the bell just follows upon the pulling of the cord. Now, it is not the case that the bell's ringing is qua ringing a function of the pulling of a cord qua cord [these concepts operate at the level of logos]; rather, the fact is that it is the reality of the ringing qua real [i.e., its formality] which is a function of the reality of the pulling of the cord qua reality [i.e., its formality]. And this is something perfectly given, even supposing that the ringing were not a function of the pulling of the cord. (12)

Or to paraphrase Zubiri's discussion, the ringing of the bell is apprehended as real in a primordial apprehension, the same one in which the pulling of the cord is apprehended as real. This is functionality at the level of primordial apprehension, not at the level of logos or reason, where Hume was looking. Thus the ringing of the bell is apprehended as a real function of the pulling of the cord, whether or not the pulling of the cord actually operates the bell by itself. For example, pulling the cord might just operate a switch which turns on an electric motor that in turn pivots the bell.

Functionality is functionality of the real inasmuch as it is real. In this sense it is a concept which encompasses many possible types. This formality, this "by" as such, is given in the impression of reality. Hume's whole critique is based upon the content of sensing, but he erred on the matter of formality. (13)

Understanding of the functionality of the bell ringing operation through logos and reason, e.g., through the physics of motion of the bell and clapper, the nature of sound waves, their generation through vibrations of the metal bell, and so forth, is much more difficult. So it is not surprising that if one tried to based our knowledge of reality on the achievement of certainty there, skepticism would be the natural result.

Kant was sufficiently persuaded by Hume's arguments that he concluded it impossible to fully reestablish causality in its historical role. As a result, he had to abandon causality for the purposes of speculative metaphysical reasoning such as proofs of the existence of God utilizing sense-based data from the "outside" world. Such reasoning he was compelled to base on moral arguments instead. Zubiri observes,

Speculative reason had seen, in causality, temporal determination; here we find ourselves with something different: a determination in the intelligible world—a strict causality which is only in the intelligible order. Hence, what was simply a possibility for speculative reason, is an objective reality for practical reason. Why? Because practical reason has a datum which theoretical reason absolutely lacks, the absolute datum of morality, of the will. (14)

This allows Kant to construct a transcendental metaphysics not based on the shaky ground of causal reasoning from the world of sensible experience. While rejecting Kant's metaphysics, Zubiri will take from him the notion of causality in the moral sphere—the only place where we can be sure of its validity—and the notion of that sphere as different than other experience.

V. Conclusions

Hume was correct in his observation that we do not perceive causes sufficiently well to base metaphysical conclusions about the world on them. But Hume's analysis of causality and the skeptical conclusions he draws from it are both defective because he does not recognize the three stages involved in knowledge of the world, and the unique characteristics of the first, primordial apprehension of reality. In particular, he does not realize (1) that at that level, functionality is associated with the formality of reality of impressions, not their content; and (2) that reality in the most fundamental sense is given to us directly—there is no need (or even possibility) of causal chains to reach it. Hume attempted to place the entire responsibility for connecting us to reality on the content of impressions, a burden they cannot bear. Ultimately it is functionality, not causality, that forms the basis of most of our knowledge; causality comes into play in the moral and personal sphere.