Causality, Personal Causality, and the Science/Religion Dialogue


The apparent conflict between science and religion is often viewed and argued with respect to the existence of God. In particular, demonstrations of God’s existence feature prominently in these discussions. The idea, presumably, is to show that God must exist, therefore science cannot dispense with God or theology, for that matter. Typically these demonstrations utilize causality in some form, require a certain philosophical framework, and purport to show the existence of an unmoved mover or similar entity. To be sure, this is a useful contribution to the science/religion dialogue. If God’s existence can be demonstrated in an unequivocable manner, science could not ever be regarded as the sole or perhaps even the most important source of knowledge. The question, therefore, turns on the efficacy of the proofs offered. Because they generally rely on the notion of causality in the physical world, which has been very controversial at least since the time of Hume, their value is likewise controversial. Nonetheless, causality should not be ruled out altogether, since it may be incontrovertible under some circumstances, and therefore useful. If one could identify these circumstances, and show that they are intimately associated with the idea of personhood, then the significance of the proofs as well as the whole nature of the science/religion dialogue would change.

I. Causality and Knowledge

Causality has been a fundamental concept in the history of philosophy, theology, and of science since the time of the ancient Greeks. This is due to the role (or presumed role) of causality with respect to nature, knowledge, and morality. Especially important has been the notion of real production of effects associated with causes. The importance of causality for the science/religion dialogue can scarcely be overstated. To understand it, we begin with a brief review of development and role of the notion of causality. This may conveniently be divided into five major phases, shown in Figure 1.

Phase 1. Metaphysical: causality as a principle of nature

The first phase, from the Pre-Socratics (c. 600 BC-400 BC) to William of Ockham (c. 1288-c. 1347), saw the origin and elaboration of the “classical” or “traditional” notion of causality, which was principally the work of Aristotle. During this epoch, causality was viewed as a principle of nature, valid for all things, and therefore the base of much of our knowledge. It became the fundamental explanatory paradigm for the sciences: all true or real knowledge is of causes in the strict, deterministic sense.

Aristotle distinguished four types of cause: material, formal, efficient, and final. Of these, efficient causality, that dealing with production of effects, became the most controversial. Real production of effects means that the cause actually produces the effects that we observe; it is not simply coincident with them (constant conjunction). Aristotle went beyond this, however, and made the four causes the key to all change, i.e., all that happens in the world. Correlatively, knowledge of the four causes became the source of all knowledge about the world, and philosophy itself, defined as “knowledge

Figure 1. The Five Phases of the Development of Causality

through causes”. The knowledge Aristotle envisioned was not just any kind of knowledge. It could have no admixture of uncertainty: we know in the true sense only when we know why things are the way that they are, and why they cannot be otherwise than they are. In other words, we are looking at a strict determinism both in the world and in our knowledge of it. Likewise implied is the idea that everything which happens must have a cause—the universality of causal explanation. Causality was thus elevated to the status of a metaphysical principle with universal applicability; hence it was used to make inferences about things that cannot be directly experienced.

On this basis, causality was employed in natural theology, forming the basis for many proofs of the existence of God. As it was understood, a cause really produces its effects, not merely in a phenomenological sense such as constant conjunction, but in a metaphysical sense. During this epoch, nearly all proofs of the existence of God, with the exception of the ontological argument, utilized causality as a principle of nature, and assumed that it was a universally valid principle that could be employed to reason from things of direct experience to realms far removed from that experience. The best-known type of such proofs is the cosmological argument, appropriately named because it utilizes causal reasoning about facts (deemed incontrovertible) of the cosmos to infer the existence of some type of being, such as a prime mover.1

With the Middle Ages came the need to make philosophy, and in particular Greek philosophy, deal with the new world of the great monotheistic religions and what revealed truth man has. This became especially important in the Islamic and Christian traditions. There were three problems that the integration of Greek thought and monotheistic religion entailed:

    • Creation of the world, ex nihilo, as opposed to the Greek view, according to which the world has always existed. This brought with it new problems of ontology, and of course, causality, since something must have caused the world to come into being out of nothingness—a type of causality not envisioned by the Greeks.


    • Universals, or forms. Where are they, and what reality do they have? That is, what is the reality of the formal cause? This was, in the middle ages, the battleground for the proponents of realism and for those of nominalism, and everyone in between. Realism asserts that universals, such as man, are res, things, and that these universals are present in all individuals of a species, for example. Nominalism denies the existence of universals in the world; only individuals exist, and universals such as man are the creations purely of the mind.


  • Reason and its power with respect to things. The central question has to do with the extent to which man’s power of reason, his ability to know things, reflects something absolute about them. This was Aristotle’s assumption, but it can lead to theological issues. For example, if causes are real, and have real productive power, can even God change them? This has a great impact on theological questions such as the nature of God’s omnipotence, and the existence of miracles.

The interaction of these questions focused certain questions very sharply, especially with regard to causality. Realism tends to place causality in things, in the world; whereas nominalism tended to place it in the mind. The latter approach leads to downplaying efficient causality as real production.

These questions first surfaced and were taken up by Arabic and Jewish philosophers, beginning in the East (Alkindi, 9th-10th century; Alfarabi, c. 900-950, and Avicenna (980-1037). The focus of these efforts then shifted to the West, to Moslem Spain, and especially Cordoba, where Averroës (1126-1198) and Maimonides (1135-1204) both lived. Of these philosophers, Averroës was the most important with respect to development of the idea of causality.

Averroës was a realist, and especially so with respect to causality. For him, causes have real productive powers and reflect necessary links between things, that is, between the cause and its effect. So we have here a position that has roots directly in two of the themes above: realism with respect to universals, and the power of reason to penetrate to the heart of nature and reveal how things truly are. It is to him that we owe this elaboration and clarification of the nature of causality. Causality, for Averroës, is characterized by

  • real production of effects
  • necessary connection between cause and effect
  • strict determinism (the effect must follow from the cause)
  • uniformity
  • contiguity
  • temporal priority

However, this soon led Averroës into some serious theological problems—thus impinging on the third theme—because they forced him into some difficult positions, such as his belief that the human intellect is a single, immaterial and eternal form—the only one for the entire species. Furthermore, even God cannot change the nature of things in the world as revealed to us by our reasoning and perception (as separate, distinct, real things), in particular, the relations of cause and effect; and so in this sense at least God is not omnipotent. Therefore accounting for miracles poses some difficulties, which Averroës ultimately gets around by denying that they really are miracles, just very unusual phenomena—a kind of secondary causality theory. And finally, for Averroës, motion is eternal on account of the nature of causality, and so he has an additional problem with the creation of the world. Eventually he fell into the famous “dual truth” theory, according to which something can be true philosophically and false theologically.2

In the West, Scholasticism began with St. Anselm (1033-1109), who is best known in philosophy for his proofs of the existence of God, especially what has become known as the “Ontological Argument.” Anselm was solidly in the Augustinian tradition, and was unfamiliar with the works of Aristotle, which were to become known in the West in the next century. In the Monologium, he gave proofs of the “standard” sort, based on causal arguments. In the Proslogium, he gave the “Ontological argument”, which is non-causal. Briefly, the argument runs as follows: if we say that God is an entity that is the greatest possible, then no greater entity can exist. But if God existed only in the mind, then we could imagine Him existing in reality, which is greater. Therefore we can imagine something greater than God, if he does not exist. But this is a contradiction to our premise. Therefore God must exist. Though always controversial, this argument later found use in phase two, when causal proofs could not be employed.

St. Thomas accepted the idea of real production, and believed that causes are “out there”, that we can perceive them, and that, indeed, everything that happens is caused by something. Causality, for him as for Aristotle, becomes the basis of change in the world and at the same time our knowledge of it. St. Thomas’ principal contribution to the theory of causality has to do with creation ex nihilo, which is a fact of Revelation that Aristotle never considered. Aristotle’s definition of efficient causality requires that one thing act on another, already existing thing, to bring it from potency to act. St. Thomas basically generalizes the notion of efficient causality to mean contributing being to, or contributing to the being or becoming of something else. Or in other words, efficient causality in the sense of creation does not refer to motion and applies to the entire being of the effect, whereas ordinary efficient causality has to do with motion and applies to only part of the being of the effect.3 Thus Aristotle’s efficient causality is a special case of St. Thomas’.

After St. Thomas, the next major contributor to causality is John Duns Scotus (c. 1266-1308). With Scotus, the drift of medieval thought towards nominalism and away from realism, towards a view of causality as in the mind and away from the view of it as in reality, both accelerated, reaching a peak with William of Ockham (c 1288-1347). Scotus accepted the view of causality put forth by St. Thomas more or less intact; he questioned some of the proofs based on it, however. For example, the first or prime mover is simply the cause of motion, that is, a necessary hypothesis to explain the fact of physical motion in the universe. This does not make Him (or it) the cause of the being of all things in the universe. Scotus also accepted the view that we can extract knowledge of causes (in the strong sense) from our perception of the world. He based his argument for the existence of God on causality as well, claiming that even in the case of an infinite regress of causes, “the whole series of effects would be dependent on some prior cause.”4

For Ockham, philosophy and theology are completely separate, and the idea that things, such as they are in the world, could have any influence on the Divine Will, or in any way circumscribe Divine action, is summarily rejected. This is diametrically opposite, of course, to the position of Averoës, and represents a significant downgrading of the idea that causality is about things in the world in some real sense. Ockham’s main contribution to the theory of causality is his rejection of the idea of necessity in causes, that is, his rejection of the idea that there is a necessary connection between cause and effect. He also rejects the idea that we can somehow perceive causes with the mind, falling back on the idea of constant conjunction, together with the idea that if A causes B, and A is taken away, then B also goes away, implies that A is a cause of B. Ockham rejects the “first mover” proof of the existence of God, because it cannot be shown that everything which is moved must be moved by something else. Moreover, he rejects the idea that an infinite regress of causes is possible. And he rejects the proof from finality.

Phase 2. Epistemological: causality as a principle of understanding

This second phase receives the idea of causality more or less unchanged from the first phase. But in light of the endless controversies from that phase—about nature, universals, and proofs for the existence of God, together with the manifest failure to achieve the objectives proposed, namely secure knowledge of the world—the second phase sought to construct a secure foundation for knowing, and for this it preferentially employed causality as a principle of knowing rather than a principle of nature. As a result, causality, rather than being a tool for understanding what is happening in the world, became more important with respect to the link from the world to our ideas about it. There was less interest in what is happening in the world, with respect to cause and effect, and more with respect to the problem of what causes our ideas and how we can be sure that they are adequate and convey truth to us. To guarantee this link, it becomes necessary to invoke God himself. Thus in this phase, the focus of causality shifts from investigation of things and change in the world, to justification of our knowledge about the world. This is a very significant change, though not a re-thinking of causality. Philosophers still accepted the notion of causality as developed in the classical tradition (few bought into Ockham’s critique), but they used it differently. Not surprisingly, the philosophers of this period relied heavily on the ontological argument, since it is not based on reasoning from causes in the world, and more importantly, it established the existenc of God, who can then be invoked for the above-mentioned guarantee of non-deception.

This phase begins with René Descartes (1596-1650). Descartes inherited classical philosophy in almost all of its aspects, and also its fundamental horizon of nihility. But he had a different agenda. He felt that much of the certainty about life, about knowledge, about faith, and about things, which characterized the Middle Ages, had disappeared. So he was concerned with reestablishing certainty, with building a firm foundation for knowledge and belief—in things, in the world, in God. Descartes’ procedure, as is well-known, is to begin by doubting everything that can possibly be doubted, and then gradually rebuilding knowledge on the basis of the things he believes cannot be doubted. This led him to his famous first non-doubtable principle, the Cogito, ergo sum. But Descartes needed causality to complete his task. With respect to causality, he did not dispute any of its principle characteristics. For him, as for Aristotle and most of the philosophical tradition since, a cause has power to make things happen; and he relies upon this, as unquestionably true, to help him in out of his self-imposed doubts. Specifically, he restored his confidence in his ability to know things about the world by calling upon God to guarantee the causal link from the outside world to the ideas in his mind about it:

But since God is no deceiver, it is evident that He does not of Himself, and immediately, communicate those ideas [about bodies] to me. Nor does he do so by means of some creature…For he has given me…a very strong inclination to believe that those ideas are conveyed to me by corporeal things, I do not see how He could be defended against the charge of deception, were the ideas produced [caused] otherwise than by corporeal things. We have, therefore, no option save to conclude that corporeal things do indeed exist. [Med. VI, p. 72.]

So now causality, rather than primarily being a tool for understanding what is happening in the world, is needed to guarantee the link from the world to our ideas about it.

This phase includes the continental rationalists (Spinoza, Leibnitz), and the English empiricists Locke and Berkeley. Spinoza says, “The idea of an individual thing actually existing is caused by God…” (Ethics, Prop. IX). For Leibnitz, since God created the monads, and established the harmonious working of the universe, He caused the harmony, and in particular, He caused us—human monads—to have ideas about the world which appear precisely in the order and at the time that actual changes occur there.5 Locke, like Descartes, must also call upon God to guarantee our knowledge of that world, though he does not directly invoke God to guarantee the causal link; he merely tells us that the ideas produced in our mind are adequate for the job they have to do on account of the “wisdom and Will of our Maker”.6 For Berkeley, more than just their guarantor, God directly causes our ideas of the world; this extends to observed regularities in the world, which Berkeley calls the Laws of Nature.7

Phase 3. The Philosophical Crisis of Causality, Hume, Kant, and Mill

In the third phase, David Hume (1711-1776), who remained wedded to the belief that causality can only be of the traditional, strictly deterministic variety, showed the obvious difficulties with the arguments of the first and second phases. In particular, he zeroed in on the connection between cause and effect, and thus cast doubt on the arguments of the first phase and everything that depends upon them. Hume devoted considerable effort to uncovering the psychological basis for our belief in causality, in the strong, classical form. He believed that he had found it in the fact that what we term ‘causes’ are always found to be conjoined to their effects, and as a result, the mind eventually forms some sort of connection between the two ideas, which in addition have the properties of contiguity and temporal sucession.8 For Hume, there is no perception of any link or connection between a cause and an effect:

Should anyone…pretend to define a cause, by saying it is something productive of another, it is evident he would say nothing. For what does he mean by production? Can he give any definition of it, that will not be the same with that of causation? If he can, I desire that it be produced. If he cannot, he here runs in a circle, and gives a synonymous term instead of a definition.9

The conclusion is that insofar as true knowledge of causes is possible, we can have apodiectic or metaphysical knowledge; but insofar as our knowledge of causes resolves into constant conjunctions, “true” knowledge about the “external” world, and a fortiori metaphysical knowledge, is impossible:

If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matters of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.10

This, presumably, also applies to the Ontological Argument. But Hume still has a use for causality. Hume explicitly accepts three of the classical characteristics of causality: temporal priority,11 contiguity,12 and uniformity (which he terms “necessity”). It may seem surprising at first sight that he would retain this latter; but for him, it is related to the idea of causes as constant conjunction. And, he wished to extend the idea to the moral arena, so that morality becomes nothing more than a tendency to always associate certain activities with certain “pleasing sentiments of approbation”. Hume wants to make all causes necessary—i.e., deterministic or uniform—to avoid any possibility of something “occult” —some unknown power or agency—coming into the picture.13

Kant (1724-1804) felt that Hume’s attack on causality was so destructive of knowledge that he had to reestablish it in a secure way. Because he assumed that science requires causality in the traditional sense, he sought to reconstitute it on the basis of his theory of the mental life as synthesis according to the categories. That is, Kant believed that the usual statement of causality, “every event has a cause,” is a necessary and universal truth. In the end, 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.

Kant noted that some truths are known through morality, in the sense that certain actions are known to be right or wrong without need for any type of causal reasoning based on natural laws or empirical observations. Morality is unconditional because it is intelligible “in itself”, and man is something knowable in the fullest sense (unlike physical objects). Thus moral knowledge is more secure than knowledge of the external world. This moral knowledge is impressed on man’s conscience; in Kant’s terminology:

…the moral law, although it gives no view, yet gives us a fact absolutely inexplicable from any data of the sensible world, and the whole compass of our theoretical use of reason, a fact which points to a pure world of the understanding, nay, even defines it positively and enables us to know something of it, namely, a law.14 [Italics added]

This law, of course, points to a law giver. If one accepts the general Kantian approach that moral knowledge is more secure than knowledge of the external world, or equivalently, if one believes for another reason that certain moral imperatives (or facts) are absolute, there would be reasons to question the any philosophical position (such as the omnicompetence of science) that denies this absolute character. 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.15

This allowed Kant to construct a transcendental metaphysics not based on the shaky ground of causal reasoning from the world of sensible experience:

Ultimately, Kant’s transcendental metaphysics is the transcendental metaphysics of something immanent: the transcendental metaphysics of the person....It is a Metaphysics in which reason, by means of concepts, reaches the objective reality of the thing-in-itself, to wit, immortality and God.16

John Stuart Mill (1806-1873), attempted to modify Hume’s theory of causality as constant conjunction so that it could serve as the basis for empirical science. For Mill, the various uniformities found in nature we term the “laws of Nature”. He was especially interested in what he terms the process of induction, which is how scientific laws are created from observation, experiment, and other sources. He is also interested in the reasoning processes by which conclusions are deduced from those laws, and other aspects of the reasoning that takes place in the conduct of science. For this, he believes that uniformity of nature and the law of cause and effect are both requisite. He explicitly tells us that he has no interest in metaphysical questions and inferences based on causality. Mill’s remarks make clear the shift in emphasis from pure philosophical speculation about causality, to an understanding of it based on the process and outcome of science:

I make no research into the ultimate or ontological cause of anything….the causes with which I concern myself are not efficient, but physical causes. They are causes in that sense alone, in which one physical fact is said to be the cause of another. Of the efficient causes of phenomena, or whether any such causes exist at all, I am not called upon to give an opinion.17

Mill demonstrates his empiricist heritage when he also rejects the idea of any force or power between objects:

The notion of causation is deemed…to imply a mysterious and most powerful tie, such as cannot, or at least does not, exist between any physical fact and that other physical fact on which it is invariably consequent, and which is popularly termed its cause: and thence is deduced the supposed necessity of ascending higher, into the essences and inherent constitution of things, to find the true cause, the cause which is not only followed by, but actually produces, the effect. No such necessity exists for the purposes of the present inquiry….The only notion of a cause, which the theory of induction requires, is such a notion as can be gained from experience.18

This notion Mill attributes to “that invariability of succession…found by observation to obtain between every fact in nature and some other fact which has preceded it.”19 In this respect, Mill is rejecting Kant’s notion of causality and returning to something akin to Hume’s views, at least with respect to the origin of belief in any causal connection.

Mill inherited from classical philosophy the belief that causal regularity is the foundation of all rational understanding. On the other hand, in light of Hume’s arguments and Kant’s criticism of Hume, he does not want to commit himself to a closed empiricist perspective; there are too many problems with Hume’s view, especially. The question that he wishes to ask is, “What do I really need from the law of causality in order to conduct science?” To answer this question, he tells us, “The truth that every fact which has a beginning has a cause is coextensive with human experience.” Recognition of this universal truth, he contends, “is the main pillar of inductive science”. So the procedure of science is this: by induction, that is, generalization from uniform experience, causal laws are inferred. Since every event must have a cause, these laws can then be used to make predictions. Mill’s belief in strict, deterministic Newtonian physics is revealed by his reference to what has since become known as “Laplace’s demon”:

The state of the whole universe at any instant, we believe to be the consequence of its state at the previous instant; insomuch that one who knew all the agents which exist at the present moment, their collocation in space, and all their properties, in other words, the laws of their agency, could predict the whole subsequent history of the universe….And if any particular state of the entire universe could ever recur a second time, all subsequent states would return too…20

So for Mill, the last major thinker on causality prior to the upheavals of the 20th century, most of the major pillars of causality were still intact: determinism, universality, contiguity, and temporal priority. The focus is still on causality as the basis for our knowledge of the world, though Mill is ambivalent about his “facts” and whether they are about things in the world.

However, since causality is no longer considered to be a metaphysical principle universally valid for things, it cannot be used in the “old” way (the cosmological argument) to prove the existence of God. Hume and Mill, therefore, rejected proofs of God’s existence. Kant recognized that we have other sources of knowledge, and while rejecting the cosmological proofs, argued that we can infer God’s existence based on our knowledge of ourselves, and specifically, of our knowledge that we can cause things to happen in the traditional sense of production of reality. This, of course, represented another but lesser-known “Copernican revolution” in Kant’s philosophy.

Phase 4. The Scientific Crisis of Causality in the 20th Century

In the fourt phase, the very dev

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