Scientific truth is well-defined for 2300+ years: “Research is in fact a continuous discussion of the consistency of theories: formal consistency insofar as the discussion relates to the logical cohesion of what is asserted in joint theories; material consistency insofar as the agreement of observations with theories is concerned.” (Klant)
Not all economists got the message. Robert Aumann, for instance, maintains: “In my view, scientific theories are not to be considered ‘true’ or ‘false.’ In constructing such a theory, we are not trying to get at the truth, or even to approximate to it: rather, we are trying to organize our thoughts and observations in a useful manner.” (See intro)
Robert Aumann is in NO position to redefine science. Either his contributions are materially and formally consistent or he is OUT of science.
Aumann, though, is not an isolated case. The major approaches ― Walrasianism, Keynesianism, Marxianism, Austrianism ― are mutually contradictory, axiomatically false, and materially/formally inconsistent. Therefore, both Orthodoxy and Heterodoxy, are OUT of science.
The general public thinks that economics is a science because each year a prize is awarded that bears the title: “Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel”.
Of course, the Bank of Sweden is in NO position to redefine science. Economics is materially/formally inconsistent from Adam Smith to Robert Aumann and because of this, the economics Nobel is a willful deception of the general public.
It is of utmost importance that the term ‘Economic Sciences’ is deleted from the Prize’s title as fast as possible because there is NO such thing. Economics is for 200+ years now OUT of science.
Related 'What is so great about cargo cult science? or, How economists learned to stop worrying about failure' and 'The tragicomedy of Heterodoxy' and 'Economics’ lack of scientific legitimacy' and 'Feynman Integrity, fake science and the econoblogosphere' and 'True macrofoundations: the reset of economics'
You ask: “When has the ‘truth’ ever been discovered by science?”
There is no need to put truth in quotation marks. Scientific truth is well-defined since 2000+ years and scientists are rather good at producing the stuff, in contradistinction to economists who are merely good at producing blather. This applies to both orthodox AND heterodox economists.
Walrasianism, Keynesianism, Marxianism, Austrianism is provably false. Provably false means false in the SAME way false as the geocentric theory is false, that is TOTALLY false, that is, logically and empirically false. The consequence is that economics is OUT of science just as the flat-earth theory or the phlogiston theory are out of science.
From this follows that the major approaches have to be thrown out and FULLY replaced just as the geocentric paradigm had to be fully replaced with the heliocentric paradigm.
Economics as we know it is one of the most annoying constructs since the ancient Greeks invented science but the representative economist has no clue of how to get out of the self-produced mess. For lack of the true theory, he resorts to excuses#1 and subscribes to the pluralism of false theories.
Economics is out of science, the representative economist is out of science, Lars Syll and Henry are out of science. The simple truth is that all this has NOTHING to do with the complexity of economic reality#2 but with the utter scientific incompetence of economists.
#1 Failed economics: The losers’ long list of lame excuses
#2 Complexity and stupidity