Philosophy of Causation – Vol. 2 – Middle Ages

The second part of the written part of my Special Comprehensive Exam takes us back to the Middle Ages. It proves that by no means it was a dark age, and that the modern science has its important predecessors in those working in the field of natural philosophy at that time. My summary gives a small insight into the complexity  of their ideas, and the importance of the causal reflection in their explanations.

Causality in Middle Ages

The first important center of science and philosophy in Middle Ages was located in Oxford. Its main representatives followed the Pythagoreans and Plato, fostering mainly the mathematical component. They searched for explanations in mathematical terms, trying to relate them to Aristotle’s causality.

robert-grosseteste-1-sizedOne of the first thinkers of that school, Robert Grosseteste (ca. 1168-1253), who tried to emphasize both the role of mathematics and the indispensability of experience and experiments (“in thought if not in deed”), which are supposed to verify or falsify the outcomes of physics. But he did not present any procedure of verification. It is also doubtful that he made real experiments. He would value a demonstration involving all four causes, but he thought they should be somehow quantifiable and amenable to mathematical treatment. (He presents an analysis of four causes of thunder: 1) the formal cause is “rumbling sound in clouds,” 2) the material cause is “quenching of fire in cloud,” 3) the efficiency involved is described through the mechanism that produces the thunder (clouds, vapor, fire in air), 4) the final cause (according to Pythagoreans) is to terrify those detained in the infernal regions.)

download=176443-Cook_Roger-BaconRoger Bacon (ca. 1214-1294) was a disciple of Grosseteste. He claims that mathematics is not only essential for understanding all sciences. Without it we are not able to understand the world. Although, following his teacher, he states that mathematical reasoning must be supplemented by experience to make its intuitions certain, it is again questionable whether he performed real experiments. But it needs to be noticed that he, supported by John Peckham (ca. 1230-1292), brought an important contribution to optical sciences (even if their appeal was more towards experience than experimentation). They were also committed to a realist philosophy of science and were looking for causes of phenomena.

William_of_OckhamThe 14th century science at Oxford further questioned realism and remained under the influence of the nominalism of William of Ockham (ca. 1287-1347), who would challenge the reality of Aristotelian “common natures.” Terms such as quantity, motion, time, space, velocity and causality, had for him no other real referents than an individual substance. In this situation only the mathematical approach was able to survive (it developed analyses similar to those employed in 17th century science), while the experimental and causal components were somehow neglected. This turn brought a development of calculatory techniques and kinetics. Indeed, it was the Medieval Oxford where an important development of the philosophy of motion was reached by a series of thinkers such as: Ockham, who associated motion with successive positions of body in motion (res relativa, forma fluens); Walter Burley (ca. 1275-1344), for whom motion was res successiva, that is something real, over and above moving object, having its causes and effects (not only forma fluens but also fluxus forme); Thomas Bradwardine (ca. 1290-1349), who equated motion with “speed of motion,” and thus brought a mathematization of motion; William Heytesbury (before 1313-1372/73), who introduced important kinematical rules called “mean-speed theorem;” and Richard Swineshead (fl. ca. 1340-1354), who is associated with an anonymous Tractatus de motu locali difformi, in which we find a description of four causes of local motion: “the material cause of motion, or the matter of motion, is whatever is acquired through motion; the formal cause is a certain transmutation conjoined with time; the efficient cause is a ratio of greater inequality of the moving power over resistance; and the final cause is the goal intended.”

The other center of medieval philosophy and science was located in Paris and remained in an opposition to Oxford. Its main thinkers did not trust mathematics as much as the empirical temper of Aristotelian tradition (rediscovered at the University of Paris). They believed in man’s ability both to come to know the world of nature and to discover and name the causes of its phenomena. Thus, it was the academia in Paris that gave start to the reflection on dynamical problems, supporting the origin of a systematic science of mechanics, which already had its kinematic component established at Oxford.

AlbertusMagnusThe philosophical foundation of the Paris movement was offered by Albert the Great (1193/1206-1280) and his ingenious pupil Thomas Aquinas (1225?-1274). The first one of them, a leading scientist of his time, emphasized the role of observation and empirical reasoning. He saw the object of mathematics being an abstracted entity rather than an ontologically antecedent form. He emphasized the importance of the search for causes of natural things in the oft quoted passage from his De cello et mundo in which he says that: “In natural science we do not investigate how God the Creator operates according to His free will and uses miracles to show His power, but rather what may happen in natural things on the ground of the causes inherent in nature.”

Aquinas’ great contribution was his explanation of the way in which all four causes can be used in the demonstration in natural science. In his commentaries on major philosophical works of Aristotle Aquinas brings important development of the theory of four causes. He lists four types of formal causality, and introduces the distinction between essentia (essence, Aristotelian prime matter informed) and esse (existence). Following Avicenna, he defines four types of efficient causation and introduces important distinctions between principal/instrumental, and primary/secondary causes. He explains the way in which one thing can have many per se causes, cases of reciprocal causation, and those of things being causes of contrarieties. He also develops Aristotle’s reflection on the modes of causation, and provides an important commentary on Philosopher’s doctrine of necessity and chance. He shows that the problem of a chance event described in terms of two lines of causality crossing at a certain point of time and space cannot be resolved by tracing back each line of causality. Such operation will not provide an answer to the question of the proper (per se) cause of a chance occurrence.[1]

Developments of philosophy of causation presented by Albert the Great and Thomas Aquinas encouraged others to embrace more consciously and ardently philosophical realism in their science. Peter of Maricourt (fl. 1269) was a great experimenter who named magnet’s poles after the celestial poles and developed a methodology of falsification. Theodoric of Freiburg (ca. 1250-1310) who was a Dominican Friar concentrated himself on the search for the causes of rainbows and radiant phenomena. Although he emphasized the importance of all four causes in scientific explanation, he concentrated mainly on material and efficient causes. In his study of rainbows, he made an attempt on duplicating natural processes under controlled conditions, and thus gave the foundation to laboratory experiments. He also challenged Aristotle proposing his own use of induction which brings him closer to the modern experimental method than anyone else at his time.

The condemnations of Aristotle of 1270 and 1277 in Paris gave a fresh impulse to construct new hypothetical schemata for “saving the phenomena.” This brought a new realist analysis of local motion, developed by Jean Buridan (ca. 1310-after 1358), who claimed that it is real and independent of the thing moved and the place, and spoke of a virtus derelicta (“force left behind”) which he called impetus; Albert of Saxony (ca. 1316-1390), who speculated on the doctrine of impetus and the cause of the acceleration of falling bodies; and Nicole Oresme who would address the same problems in his writings. Interestingly enough, all three of them sowed seeds of the Copernican revolution, saying that both the hypothesis of earth in rest and the one with earth in motion, save the phenomena (but they refused to develop the second opinion). Oresme was also the first to develop an analogy between the workings of a clock and the universe, the analogy which would return and become very powerful with the mechanical turn in science.

Middle Ages brought one more opinion on causality, which remained in a radical opposition to the developments proposed in Oxford and Paris. Medieval occasionalism, linked to kalām, which is a type of philosophizing in Islam, developed by Al-Ash‘arī (d. 935) and Al-Ghazālī (1058–1111), denied any kind of causation in creatures, attributing it to the only true agent, God. This position was opposed by Averroes and Aquinas who argued that it deprives natural things of the actions that belong to them.

This story shows the ways in which the philosophy of causation, which had its roots in antiquity, was developed in Middle Ages. This movement prepared the stage for the Renaissance and the origin of the classical science, philosophy, and methodology which brought a dramatic change in philosophy of causation and more generally in philosophy of nature and metaphysics. I will describe them in the third episode which will be coming soon. 🙂


Philosophy of Causation – Vol. 1 – Ancient Greece

I have recently accomplished my Special Comprehensive Exam which is a major step on the way of my doctoral studies at the GTU in Berkeley, CA. The first part of the project was a written exam which covered some of the major developments of the theory of causation in ancient, medieval, and modern philosophy. In this post I publish the first part of the exam, the one referring to the ancient tradition. I hope the readers of my blog will find it interesting. Remaining parts are to come soon.


The development of the reflection on causality in ancient Greece has its beginnings in the philosophy of early Milesians, who presented three positions on the problem of change in nature. According to the first and predominant option some things change (totally or in some ways), while other things do not go through the process of change. Noticing this, some of the philosophers looked for a fundamental principle which does not change and remains constant. Thus, we can say that they gave the origin to the reflection on material cause. Thales (620-550 BC) claims that the fundamental constituent which remains unchanged is H2O. It can exist as solid, liquid or vapor. Hence, all things are water in various states. Anaximenes (570-500 BC) takes air for the basic stuff and says that everything is really air in different forms of rarity or density. Anaximander (610-525 BC) takes an important step saying that none of the basic elements (earth, fire, water) can be the first principle for it would destroy other elements. He enters a meta-level of philosophical reflection saying that the undetermined principle is most fundamental and may be called “the infinite.” It is by joining and separating of opposite qualities present in “the infinite” that all things come into being and change. (Michael Dodds rightly says that if we substitute “energy” for “air,” Anaximenes becomes Einstein. Heisenberg saw Anaximander’s “infinite” equivalent to “energy” in modern physics. Dodds argues that his description is closer to Thales: instead of H2O we have “matter” or “energy.”)


The second view of change among early Greek philosophers is represented by Heraclitus (fl. 500 BC) and assumes that all things are constantly changing. Things are just ephemeral patterns of continuity in the perpetual flux of the world. (Dodds finds this position similar to the contemporary philosophy of process). The third view represented by Parmenides (fl. 500 BC) remains in opposition to the former one, as it assumes that nothing really changes in nature. Things either “are” or “are not,” there is no other option, and thus nothing can change. For a new thing could come into being only from non-being (which is impossible), or from being (which would mean that it existed before). Therefore, change is an illusion.

The conceptual level of Anaximander’s reflection (as distinct from more empirically grounded philosophy of other Milesians) finds its continuation in Anaxagoras (c. 510-428 BC), who declares cosmic intelligence (mind, nous) to be what causes everything. But since intelligence seeks what it values, this kind of explanation exceeds an interest in material cause, predominant among Anaxagoras’ predecessors, entering the new level of explanation, which is teleological in style. Hence, we can find here the first primitive notion of final causation. However, Plato (Socrates in Phaedo) claims that the details of Anaxagoras’ reflection show that he was not aware of this commitment (he concentrates mainly on materialistic factors such as air, water, and vortex).

The further step on the way of defining causality was taken by Empedocles (ca. 495-435 BC) who presents the first reflection on efficient cause. He claims that besides the elements of earth, air, fire, and water, two further elements, “love” and “strife” are needed in order to combine or keep apart the basic elements. The idea of efficient cause was developed later on by Democritus (ca. 460 – ca. 370 BC) and atomists, who would remain in opposition to the idea of final cause of the universe, arguing in favor of the purely mechanical view of causation (movement and collisions of atoms).


Among the earliest philosophical schools we find one more which remains at odds with those described so far. It is the school of Pythagoras (ca. 570- ca. 490 BC), who was the first to make an attempt to understand the cosmos and its phenomena in terms of number. His reflection was rooted in Egyptian geometry and Babylonian arithmetic. Pythagoras used them to develop a philosophy of nature based on mathematics. He suggested a parallelism between the idealizations of geometry and the physical patterns of the universe. According to him, number underlines all physical objects and its study reveals deeper level of reality than is apparent on the surface. Aristotle would say, later on, that Pythagoreans considered number to be the principle of both matter (even or “unlimited” elements of number) and form (uneven or “limited” elements of number). Thus, every physical entity is explainable in terms of mathematics. From this basic point the Pythagoreans went to a detailed study of mathematical proportions, harmonic relationships, and irrational numbers, which gave the origins to a study of continuum and infinite divisibility.

Penrose tiles

Pythagorean ideas combined with Democritus’ atomism inspired Plato (428/427 or 424/423 – 348/347 BC) to present his geometric theory of matter. The originality of his theory is based on the fact that he regards matter (“the mother of all becoming”) as a stable and eternal receptacle for Ideas of Forms, and thus formulates the first notion of formal causation. He is also probably the first one to state explicitly the principle of causality in Timaeus: “everything that becomes or changes must do so owing to some cause; for nothing can come to be without a cause.” For Plato the world accessible to our sensual experience is changing and made of appearances. It is merely a shadow of the true reality which is the world of autonomous and immaterial Forms. If the formless matter is “the mother,” the eternal form is “the father,” and the transitory phenomena known to our senses are their offspring. The elements of the physical world are construed on the model of geometrical patterns: fire takes the shape of tetrahedron, air of octahedron, and water of icosahedron. All of these shapes are made of multiplied triangles. Therefore, the triangle can be regarded as an atomic element in Democritean sense.

What remains crucial for our further reflection is the fact that neither Pythagoras nor Plato regarded mathematics, as did Aristotle, as a formal and abstract discipline which applied to reality enables us to construe a subalternated type of scientific knowing, abstracted from empirical and sensual experience. They saw it rather as a way of arriving at the ultimate and basic reality itself, which in sensual experience is given only in ephemeral appearances.


Aristotle (384-322 BC) presents the most developed theory of causation among philosophers in ancient Greece. He systematizes and further develops the teaching of his predecessors, defining four kinds of causality in Posterior Analytics, Physics, and Metaphysics (he alludes to various causes in other works as well). Material cause for Aristotle means not only the basic building stuff. He introduces the term of primary matter (prōtē hulē) which he understands as a principle of potentiality, something that persists through all changes that a given substance can be exposed to (something that constitutes the very possibility of being a substance at all). Concerning formal cause, Aristotle remains in a radical opposition to the transcendental character of Ideas in Plato. For him forms must be in things, determining their actuality. Formal cause answers the question “why” something is the kind of a thing it is, and it cannot be reduced to “shape” or “appearance” of a thing. Aristotle introduces also an important distinction between accidental and substantial form, which he explains in terms of changes that effect in an “alteration” (an accidental change), which does not change the substantial principle of a substance, as opposed to a situation in which the thing changes as a whole (coming-to-be of a new substance). For Aristotle material and formal types of causation are intrinsically related. They can be separated only in mental reflection. In reality we know primary matter only as informed, and form only as informing primary matter.

The other two causes indispensable for Aristotle’s description of reality are: efficient and final. The former one is generally defined as an activity of an agent bringing motion or rest. However, Aristotle classifies as efficient causality also activities such as giving an advice, which in some of its aspects goes beyond physical interaction and exchange of energy. The latter, final cause, he defines as “that for the sake of which” a thing is done, or a good proper for a thing that can be attained. It is important for him to notice that final causality should not be associated merely with conscious and rational human decisions. He speaks about natural teleology which is present both in inanimate and animate nature even if it “does not deliberate.” Finally, Aristotle emphasizes the relation between efficient, formal, and final causation, noticing at the same time that final cause is the first and should be regarded as causa causarum.


Aristotle devotes no less than three chapters of the second book of Physics to the study of chance and necessity. He criticizes philosophers of the past for either not finding a place for chance on their list of causes, or not paying enough attention to it. He refers specifically to Empedocles who attributed to chance certain events, such as movement of air in the process of the separation of elements, or the origin of the parts of animals, but did not analyze the nature of chance in more detail. He is also critical about Democritus who attributed the origin of the universe to spontaneity, claiming at the same time that chance is not responsible for the generation of plants, animals, or mind. Such an explanation ascribes the causes of things to both necessity and chance, understood as the “absence of purpose.” Following this line of thinking, Plato (Timaeus) saw both necessity and chance as inherent in the material cause, which is formed by the Demiurge (reason) who strives to prevail over necessity of matter resistant to order. Because the reason cannot succeed fully in its endeavor, chance events occur which show no order.

Contrary to Empedocles, Democritus, and Plato, Aristotle claims that necessity, which implies order, is irreconcilable with chance, which occurs contrary to a given order. Thus, Aristotle distinguishes chance events from occurrences that happen necessarily, and those happening in the same way for the most part. Chance events also have a unique character in his second classification, in which Aristotle distinguishes between events that come to be for a purpose (due to a deliberate intention or as a result of nature), and those that do not happen for a purpose. He says that “even among the things which are outside the necessary and the normal, there are some in connection with which the phrase ‘for the sake of something’ is applicable. (…) Things of this kind, then, when they come to pass incidentally are said to be ‘by chance’.” In reference to his distinction between per se and per accidens causality Aristotle states that chance is an unusual accidental cause, and as such it is inherently unpredictable, although it still falls in the category of events that “happen for the sake of something.” Although chance events are due to nothing in the substance or per se cause which happens to concur with these unexpected occurrences, as an accidental cause, chance occurs always and only in reference to per se causes. Therefore, chance occurrences for Aristotle are always posterior and inherently related to nature (φύσις) and intellect (νοῦς). Hence, they are associated with formal and final causality rather than material necessity.


The ancient philosophical reflection on causality notes one last important contribution brought by Stoicism (3rd cen. BC), which would have a major influence on the development of modern accounts of causation. Stoics linked causality with exceptionless regularity and necessity. We can list five of their most basic theses concerning causation: 1) Cosmos is an organism imbued with divine reason (logos) and ordained by fate; 2) Nothing happens without a cause; 3) Causation involves exceptionless regularity; 4) All particular events necessitate their effects; 5) There is a fundamental distinction between external and internal causes. The last rule seems to be an answer to a controversy concerning human freedom which appears to be undermined in Stoicism (Cicero, De fato). An external cause is only auxiliary and proximate while an internal cause is called principal and perfect. Every human action is a response (based on internal cause) to an external cause producing sense-impressions. The consistency of this theory is questionable, and the action of human being in Stoicism seems to depend entirely on determinism of nature and fate.

Summing up, we can see that the ancient tradition offers a variety of approaches to the problem of causation. It developed a fourfold division of causes defined by Aristotle which will prove to have a substantial influence on medieval philosophy of nature and its steps towards understanding of the world and its processes, opening the way to natural science of modernity.