Editing Ernst Mach (section)

===Empirio-criticism<!--'Empirio-criticism' and 'Empiriocriticism' redirect here-->===
From 1895 to 1901, Mach held a newly created chair for "the history and philosophy of the inductive sciences" at the University of Vienna.{{efn|name=historiography}} In his historico-philosophical studies, Mach developed a phenomenalistic [[philosophy of science]] that became influential in the 19th and 20th centuries, '''empirio-criticism,'''<!--boldface per WP:R#PLA--> a rigorously [[positivist]] and radically [[empiricist]] philosophy established by the German philosopher [[Richard Avenarius]] and further developed by Mach, [[Joseph Petzoldt]], and others, according to which all we can know is our sensations.{{sfn|Bunnin|Yu|2008|p=405}}

Mach originally saw scientific laws as summaries of experimental events, constructed for the purpose of making complex data comprehensible, but later emphasized mathematical functions as a more useful way to describe sensory appearances. Thus, scientific laws, while somewhat idealized, have more to do with describing sensations than with reality as it exists beyond sensations.{{efn|name=selections}}

{{cquote
|The goal which it ([[physics|physical science]]) has set itself is the ''simplest'' and ''most economical'' abstract expression of facts.

When the human mind, with its limited powers, attempts to mirror in itself the rich life of the world, of which it itself is only a small part, and which it can never hope to exhaust, it has every reason for proceeding economically.

In reality, the law always contains less than the fact itself, because it does not reproduce the fact as a whole but only in that aspect of it which is important for us, the rest being intentionally or from necessity omitted.
}}

{{cquote|In mentally separating a body from the changeable environment in which it moves, what we really do is to extricate a group of sensations on which our thoughts are fastened and which is of relatively greater stability than the others, from the stream of all our sensations.

Suppose we were to attribute to nature the property of producing like effects in like circumstances; just these like circumstances we should not know how to find. Nature exists once only. Our schematic mental imitation alone produces like events.
}}

Mach's positivism influenced many Russian [[Marxist]]s, such as [[Alexander Bogdanov]].{{sfn|Steila|2013|p=}} In 1908, [[Vladimir Lenin|Lenin]] wrote a philosophical work, ''[[Materialism and Empirio-criticism]]'',{{sfn|Lenin|1909}} in which he criticized '''Machism'''<!--boldface per WP:R#PLA--> and the views of "[[Russian Machism|Russian Machists]]". His main criticisms were that Mach's philosophy led to [[solipsism]] and to the absurd conclusion that nature did not exist before humans:

{{cquote| If bodies are "complexes of sensations," as Mach says, or "combinations of sensations," as Berkeley said, it inevitably follows that the whole world is but my idea. Starting from such a premise it is impossible to arrive at the existence of other people besides oneself: it is the purest solipsism.

...if [Mach] does not admit that the "sensible content" is an objective reality, existing independently of us, there remains only a "naked abstract" I, an I infallibly written with a capital letter and italicised, equal to "the insane piano, which imagined that it was the sole existing thing in this world." If the "sensible content" of our sensations is not the external world, then nothing exists save this naked I engaged in empty "philosophical" acrobatics.|source=Chapter 1.1, "Sensations and Complexes of Sensations"}}

In accordance with empirio-critical philosophy, Mach opposed [[Ludwig Boltzmann]] and others who proposed an atomic theory of physics. Since one cannot observe things as small as atoms directly, and since no atomic model at the time was consistent, the atomic hypothesis seemed unwarranted to Mach, and perhaps not sufficiently "economical". Mach had a direct influence on the [[Vienna Circle]] philosophers and [[logical positivism]] in general.

Several principles are attributed to Mach that distill his ideal of physical theorization, called "Machian physics":
# It should be based entirely on directly observable phenomena (in line with his positivistic leanings){{efn|name=machianview}}
# It should completely eschew [[absolute space and time]] in favour of [[relative motion]]{{sfn|Penrose|2016|p=753|ps=: Mach's principle asserts that physics should be defined entirely in terms of the relation of one body to another, and that the very notion of a background space should be abandoned}}
# Any phenomena that seem attributable to absolute space and time (e.g., [[inertia]] and [[centrifugal force]]) should instead be seen as emerging from the distribution of matter in the universe.{{sfn|Mach|1919|p=|ps=: [The] investigator must feel the need of ... knowledge of the immediate connections, say, of the masses of the universe. There will hover before him as an ideal insight into the principles of the whole matter, from which accelerated and inertial motions will result in the same way.}}

The last is singled out, particularly by Einstein, as "the" [[Mach's principle]]. Einstein cited it as one of the three principles underlying [[general relativity]]. In 1930, he wrote, "it is justified to consider Mach as the precursor of the general theory of relativity" and "the whole direction of thought of this theory conforms with Mach's".<ref>Einstein, Albert (1973). Albert Einstein to Armin Weiner, September 18, 1930, unpublished letter from the Archives of the Burndy Library in Norwalk, Connecticut, cited by Holton, Gerald J. "Where is Reality? The Answers of Einstein." In ''Science and Synthesis'', pp. 55. Edited by UNESCO. Berlin: Springer Verlag, 1971. Reprinted in ''Thematic Origins of Scientific Thought: Kepler to Einstein''. Cambridge: Mass.: Harvard University Press. p. 55.</ref>{{sfn|Pais|2005|p=283}} Einstein further reported that he had read [[David Hume]] and Mach's work "with eagerness and admiration shortly before finding relativity theory" and that "very possibly, I wouldn't have come to the solution without those philosophical studies".<ref>{{cite book |editor1-last=Stadler |editor1-first=Friedrich |title=The Present Situation in the Philosophy of Science |date=2010 |publisher=Springer Netherlands |page=349}}</ref> Before his death, Mach apparently rejected Einstein's theory.{{efn|name=preface}} Einstein knew his theories did not fulfill all Mach's principles, and no subsequent theory has either.{{cn|date=February 2025}}