The belief concerning the causal characteristics of the material world is one of the basic ones. It is possible to adopt a standpoint like the philosopher David Hume (1711-1776), and to assume that causal relationships are only a product of our mind because they cannot be derived from empirical data. Hume believes it is impossible to discover empirically in the world any relation between phenomena that could be called causality. Causality is but a name for a human custom that connects phenomena frequently succeeding each other. According to Hume, cause and effect are considered as mere successions, not as inner causal connections. In this case, science in the modern sense is possible only as a simple description.
The second option is to suppose the objective character of causal relations without being able to present an unambiguous argument; we remain at the level of metaphysical assumption, supported if not by arguments, then by the experience not only of individuals, but also historical experience and the results of science as well as individual practice. The discussion concerning the topic then has meaning only in relation to this; in other cases it will always lead to a situation where there are two opposing claims without the possibility of one decisive argument. We have selected the latter option and we consider it useful to restate the fact here, particularly because there is a rather widespread fallacy in definitions of causality and determinism that quite precludes the understanding of what is going on in contemporary science in this field. This fallacy, briefly expressed, consists in the identification of causality with determinism in a naive assumption that if there is a cause for something, it must be deterministic. The speculation then usually quickly proceeds on the presumption that there is some cause for everything; the whole universe and everything in the world are thus deterministic. To those who turn to etymology and refuse to give up the predetermination of everything that has its cause, we can offer what might seem to be a play on words, but one that is in this case very useful. The point is that we can distinguish between the expressions determined and deterministic.
Cause and Effect
Let us start step by step, however, from causality. What we understand by causality is the relation of material elements or systems, when the change of a state in one of the systems—the cause—neces- sarily elicits the change of a state in the other system—the effect. The elementary causal relation cause-effect is a certain abstraction that cannot be found in such isolated form in nature. What is closer to reality is the idea of a concatenation of causes and effects with which a range of philosophers work—from Aristotle (the hierarchical model of the world from the first cause to the purpose of all purposes) up to the mechanical materialists who aim to trace in the initial causes through their effects all the states the universe gradually acquires. Even this is, however, to a certain extent, a simplified notion counting on the presumption that one and the same cause always elicits an identical effect and that it will never be different. Another approach can thus be a combination of these causal chains in a causal web along which the changes from the initial causes gradually spread. In the following step this—so far two- dimensional—web can acquire a third dimension and stretch thus from area into space, and when we add a retrospective effect to the systems in the form of original causes, we can obtain a more complex picture of causal relations in the structure of material systems.
We can call the perfect knowledge of the initial state of a system in the causal relation the complete cause; that is, a cause that always elicits an identical effect. In reality, however, such perfect knowledge often remains an ideal and we have to take into account conditions that take part in the effect. The conditions themselves cannot elicit the effect, but they can influence the progress of the process or the very initiation through which the causal relation is fulfilled.
The problems with causality, explicitly expressed in the history of philosophy by Hume, led many natural scientists and philosophers to an effort to replace such a relation in our descriptions with functionality. This particularly concerns those who were close to positivist-oriented philosophy, because the function describes the concurrent interdependence of variables, but not their history. In such a description, some or all of what is called the asymmetries of the causal relation, which in their own way reflect the history of the system, are missing—it is existential asymmetry (which expresses the current character of cause and the potentiality of effect—the nonexisting cannot be the cause of the existing), genetic asymmetry (which is the expression of the ability to elicit changes, creative activities), and temporal asymmetry (which emphasizes the fact that whatever transformation—of matter, energy, and information—is fulfilled at the maximum speed of light, which is final, and that there is thus always a nonzero interval between cause and effect, whose extent depends on the distance in which the causal relation is fulfilled and the speed at which it happens).
Determinacy and Determinism
After a brief review of causality we can define the concepts of determinacy and determinism. Deter- minacy is the dependence of the system on causes; that is, everything that has some cause is determined directly by these causes. Determinism is the opinion that we are able to predict all the effects of determined systems if we know all their causes. That is, to emphasize this difference, causality and determinacy are the objective characteristics of material structures; determinism is the view, the belief that it is possible, with sufficiently exact knowledge of the state of a system, to count and predict all its subsequent states in relation to both the past and the future. The differentiation of determinacy and determinism, however, entails significant difficulties, the basis of which is an onto-epistemological problem. The point is that it implies the idea that we can speculate on the behavior of a system in terms of its “really” happening, independently of the observer (determi- nacy), and of the behavior of a system in terms of how we can calculate it (determinism). A given problem nonetheless cannot be disposed of by such a claim. It is evident (if only from a brief glimpse at the sky and the movement of celestial bodies) that systems always behave in a certain way, entirely independently of whether we are able to find solutions for their behavior in equations or not. The question of the full and partial determi- nacy of a system then arises. A fully determined system would be such that its every state in the arbitrarily distant future would be unambiguously dependent on (regardless of whether we would be able to calculate it or not, if anyone bothered to calculate it at all) the initial conditions or the “first cause” of the given system; that is, the whole chain of causes and effects being in progress in the system would be determined in advance by the initial state. A partially determined system would then once more stabilize after each change of the state and the subsequent state would correct itself according to the changed conditions. The first cause would then “dissolve” in the succeeding generations of causes and effects until it would lose influence on the subsequent states of the system. We can decide between these possibilities either on the basis of our philosophical (or other) belief, by which we at the same time dispose of the obligation to argue, or on the basis of some data, but in that case measurements (physics) must be performed, they must be somehow processed (mathematics), and the result must be interpreted. Through this, however, we step into the field of opinion and our belief; that is, we return to determinism and the additional differentiation of the determined, so that the deterministic loses its sense and what remains is again only causality and determinism. This determinism itself then acquires various forms in history that in fact mimic the route from the full determinacy of the universe (consistentdeterminism) to indeterministic systems.
A typical example of consistent determinism is mechanical determinism, based on the successes of classical physics and the idea of the universe as a mechanism (a big and complex mechanism, but still a mechanism) that is fully, at least fundamentally, quantifiable. This view of the deterministic universe, represented most often by Pierre-Simon Laplace (1749-1827), utterly excludes coincidence from the world, or rather considers it merely a subjective fact or a result of our ignorance of the causes. It is sufficient to discover causes, and coincidences will disappear from this world.
Twentieth-Century Interrogations of Causality
The picture reveals the first lacunae at the turn of the 20th century when Henri Poincare (18541912) distinguished stable and unstable systems; he introduced the term dynamic non-integrable system and showed that most dynamic systems are of this kind. In simplified terms, the integrability of a system means that in a dynamic system, which can always be fully characterized by kinetic energy (which is dependent only on the speed of the bodies in the system) and potential energy (the mutual position of bodies, their interaction), transformations can be found such as to allow a perspective within which the potential energy can be eliminated and mutual trajectories thus neglected. It is therefore comparatively easy to find the trajectory of bodies and to define the future states of the system. Poincare shows that such variables cannot be found and that dynamic systems are non- integrable. This means that in the field of classical physics a difficulty with determinism appears. The problem has been long understood as a mathematical one and it has been expected that the problem of such systems would be solved after the device was refined. This neglect lasted until the second half of the 20th century when chaotic systems, which revived the question, started to be talked about more frequently.
In the meantime, other problems appear. Mechanical determinism, entirely in line with classical physics, does not question the possibility of obtaining information about the state of the system, because it presumes an immediate impact from a distance. This view is, however, disturbed by Albert Einstein’s (1879-1955) theory of relativity, which introduces the principle that the speed of light, which is final, is the maximum possible speed attainable in our universe. No signal can travel faster and we therefore find ourselves enclosed in the area of what is called the horizon of particles or—if we intend to place emphasis on mutual interaction—in the area of the causal horizon.
Quantum mechanics means another questioning of determinism, namely in its more moderate form. It shatters the idea of classical physics that it is possible to assume the standpoint of the observer of the system who measures required data without influencing the system itself. Werner Heisenberg’s (1901-1976) uncertainty principle in its consequences means that it is not possible to obtain simultaneously with sufficient exactitude all the decisive information (typically the energy and position of the particle) regarding the quantum system. Even though quantum mechanics thwarted deterministic ideas and for many meant a definitive rift with the mathematical predictions of the future and was also understood as the confirmation of freedom from the side of physics, there still remained numerous scientists and philosophers who believed, like Einstein, that “God does not play dice.” They were convinced, and some still are, that the impossibility of obtaining at the same time all the required data about the system is just a technical problem or that it is a question of those characteristics of reality that have so far escaped us and that the situation will improve with the development of technology and physics and that determinism will be preserved and the world will not be ruled by accident, out of which the notion of objective fact would emerge in indeterministic conceptions of some quantum physics interpretations. However, all the experiments that so far have been performed with the aim of deciding the situation, including attempts that were inspired by the thought experiments of significant followers of determinism, have proved that most probably it is not a technical problem, but that reality itself is such. So the notions determined and deterministic blend here again and it seems that the systems really are not the predetermined “first cause” once and for all. The followers of determinism can still argue through the ambiguity of the transition from the world of subatomic particles to our macroworld and rely on the fact that somewhere the rescue of the deterministic world would once again appear. This hope, however, is slowly beginning to fade with regard to the works that do not need to proceed on the basis of quantum mechanics and the uncertainty principle; they do not even require relativist physics, but they are based on the very core of classical physics, namely on dynamics in the form as experienced at the very end of the 19th century (H. Poincare). It had been presumed for a long time that this was just a problem of technical insufficiency, but since the middle of the 20th century theories have been gradually conceived that prove that even dynamic unstable systems, as defined by Poincare, show equally indeterministic behavior as, for instance, quantum systems.
The probability description, characteristic of chaotic (and quantum) systems, becomes part of science much earlier, that is, in relation to thermodynamic theory in the second half of the 19th century. It was applicable wherever it was used with systems containing a very large number of elements, so it was not possible (and as a result, as it turned out, not even necessary) to take into consideration the exact characteristics of each of them; but to determine the behavior of a system with a sufficient degree of probability it was enough to know their probable configuration. Yet because it was supposed that it would be enough to have sufficient capacity for finding all the data about each element in order to replace the probability description with an unambiguous (dynamic) one, this stochastic chaos did not disrupt the belief in determinism. The incidental behavior of such a system is influenced by external conditions, unlike dynamic chaos where the unpredictable behavior is brought about by the impossibility of estimating the initial conditions.
Similar to classical and relativistic physics when the classical model remained a good device for the description of bodies of the macroworld moving at low speeds and became a special case of relativist physics, everything gradually indicates that history will be repeated with new protagonists, and the deterministic description will remain reserved for the relatively narrow circle of simple systems and will become a special case in a more general description, which will be probabilistic.
See also Aristotle; Determinism; Albert Einstein; David Hume; Henri Poincare; Quantum Mechanics; Teleology
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