“Causality applies only to a system which is left undisturbed. If a system is small, we cannot observe it without producing a serious disturbance and hence we cannot expect to find any causal connexion between the results of our observations. Causality will still be assumed to apply to undisturbed systems and the equations which will be set up to describe an undisturbed system will be differential equations expressing a causal connexion between conditions at one time and conditions at a later time. These equations will be in close correspondence with the equations of classical mechanics, but they will be connected only indirectly with the results of observations.”

—  Paul Dirac, book Principles of Quantum Mechanics

I. The Principle of Superposition - 1. The Need for a Quantum Theory
The Principles of Quantum Mechanics (4th ed. 1958)

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Paul Dirac23
theoretical physicist 1902–1984

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“A system is a set of objects with relationships between the … in may be described generally as a complex of elements or components directly or indirectly related in a causal network, … Also, we are mainly interested in systems within which some process is continually going on, including an interchange with an environment across the boundary. It is generally agreed that when we deal with the more open system with a highly flexible structure, the distinction between the boundaries and the environment becomes a more and more arbitrary matter, dependent upon the purpose of the observer.”

Arthur D. Hall (1925–2006) American electrical engineer

Cited in: Addison C. Bennett (1978) Improving management performance in health care institutions: a total systems approach.. p. 40
A methodology for systems engineering, 1962

“The next level of causal texturing we have called the disturbed reactive environment. It may be compared with Ashby's ultra-stable system or the economists' oligopolic market.”

Fred Emery (1925–1997) Australian psychologist

Source: The Causal Texture of Organizational Environments (1963), p. 29.

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“A system in one perspective is a subsystem in another. But the systems view always treats systems as integrated wholes of their subsidiary components and never as the mechanistic aggregate of parts in isolable causal relations.”

Ervin László (1932) Hungarian musician and philosopher

Source: Introduction to Systems Philosophy (1972), p. 14.

Bernhard Riemann photo

“Kant has rightly observed that by the resolution of the concept of a thing we can find neither that it exists nor that it is the cause of something else, and accordingly that the concepts of being and causality are not analytical but can be derived only from experience. When however he later feels himself obliged to assume that the notion of causality originates in a pre-experiential property of the cognising subject and therefore stamps it a mere rule of time-series, by which, in experience, with each observation as cause any other could be connected as effect, then is the child thrown out with the bath. (Indeed, we must derive the relations of causality from experience; but we must not fail to correct and to complete our conception of these facts of experience by reflection.)”

Bernhard Riemann (1826–1866) German mathematician

Causality, p. 214
Gesammelte Mathematische Werke (1876)

Bernhard Riemann photo

“Kant has rightly observed that by the resolution of the concept of a thing we can find neither that it exists nor that it is the cause of something else, and accordingly that the concepts of being and causality are not analytical but can be derived only from experience. When however he later feels himself obliged to assume that the notion of causality originates in a pre-experiential property of the cognising subject and therefore stamps it a mere rule of time-series, by which, in experience, with each observation as cause any other could be connected as effect, then is the child thrown out with the bath.”

Bernhard Riemann (1826–1866) German mathematician

Indeed, we must derive the relations of causality from experience; but we must not fail to correct and to complete our conception of these facts of experience by reflection.
Causality
Gesammelte Mathematische Werke (1876)

Otto Pfleiderer photo

“The fundamental error of the theologians of the new faith of the present day consists in this, that they think one can without hesitation acknowledge the validity of the same scientific method in the realm of nature which they refuse to apply to that of history. … What consequence now will follow the application of the doctrine of evolution to the theological consideration of history? First of all, it is evident that it excludes miracles in every sense of the word—not merely the nature-miracle (this the men of the new faith drop without pain) but also just as much the spirit-miracle, i. e. the intervention of a foreign power in the human soul, whereby conditions are produced in it which do not result from the causal connection with antecedent conditions. If it is the methodic cardinal proposition of the science of today that we have to explain every condition as the causally determined development out of a preceding one, this excludes on principle the appearance of a condition, event, action, or personality which is not explicable out of the factors of the preceding conditions.”

Otto Pfleiderer (1839–1908) German Protestant theologian

Source: Evolution and Theology (1900), pp. 8-9.

Erwin Schrödinger photo

“The observing mind is not a physical system, it cannot interact with any physical system.”

Erwin Schrödinger (1887–1961) Austrian physicist

Nature and the Greeks (1954)
Context: The observing mind is not a physical system, it cannot interact with any physical system. And it might be better to reserve the term "subject" for the observing mind. … For the subject, if anything, is the thing that senses and thinks. Sensations and thoughts do not belong to the "world of energy."

“The object of this paper is fivefold. The first objective is to derive a practical system of demand equations which possess properties usually considered desirable from the standpoint of elementary economic theory. The second is to consider the statistical problems involved in applying the system of equations. The third is to analyse the pattern of demand for consumers' goods in terms of this system on the basis of annual data relating to the United Kingdom over the years 1920-38. The fourth is to compare the results of this system, and systems like it, with the actual state of demand in 1900. Finally, the fifth is to compare the post-war structure of demand with what might be expected from the inter-war relationshipp under free-market condition.”

Richard Stone (1913–1991) British economist, Nobel Memorial Prize winner

Stone, Richard. " Linear expenditure systems and demand analysis: an application to the pattern of British demand http://www.jstor.org/discover/10.2307/2227743?uid=3738736&uid=2&uid=4&sid=21104302232953." The Economic Journal (1954): 511-527.

Friedrich Nietzsche photo

“Between two absolutely different spheres, as between subject and object, there is no causality, no correctness, and no expression; there is, at most, an aesthetic relation”

Friedrich Nietzsche (1844–1900) German philosopher, poet, composer, cultural critic, and classical philologist

On Truth and Lie in an Extra-Moral Sense (1873)
Context: Between two absolutely different spheres, as between subject and object, there is no causality, no correctness, and no expression; there is, at most, an aesthetic relation: I mean, a suggestive transference, a stammering translation into a completely foreign tongue — for which I there is required, in any case, a freely inventive intermediate sphere and mediating force. "Appearance" is a word that contains many temptations, which is why I avoid it as much as possible. For it is not true that the essence of things "appears" in the empirical world. A painter without hands who wished to express in song the picture before his mind would, by means of this substitution of spheres, still reveal more about the essence of things than does the empirical world. Even the relationship of a nerve stimulus to the generated image is not a necessary one. But when the same image has been generated millions of times and has been handed down for many generations and finally appears on the same occasion every time for all mankind, then it acquires at last the same meaning for men it would have if it were the sole necessary image and if the relationship of the original nerve stimulus to the generated image were a strictly causal one. In the same manner, an eternally repeated dream would certainly be felt and judged to be reality. But the hardening and congealing of a metaphor guarantees absolutely nothing concerning its necessity and exclusive justification.

Gérard Debreu photo

“L. Walras first formulated the state of the economic system at any point of time as the solution of a system of simultaneous equations representing the demand for goods by consumers, the supply of goods by producers and the equilibrium condition that supply equal demand on every market.”

Gérard Debreu (1921–2004) French economist and mathematician

Arrow, Kenneth J., and Gerard Debreu. " Existence of an equilibrium for a competitive economy http://cowles.econ.yale.edu/P/cp/p00b/p0087.pdf." Econometrica: Journal of the Econometric Society (1954): p. 265

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