the myth of given is critique of foundationalist epistemology that basically asserts “data can never be given, but always be built”.
of course, nothing is simply “given” in nature. things have to be produced. (D+G would add “even production itself”).
but to go from this to “data aren’t ever real” or, worse, “data could be indefinitely different” is a stretch. analogies: a plane is produced, and is very real. a mobile phone can be produced in a myriad of forms, but they all pay respect to some invariances (you can’t make a mobile phone that violates, say, thermodynamics).
Antinomia Imediata 
Try this analogy: a phoneme needs to be articulated within a bounded, finite-dimensional space of acoustic features (it can only be so high or so low, it can only have so many different fundamental frequencies, etc.), but the number of different phonological systems that could be produced within that system is infinite, so a single acoustic “given” (in terms of those articulatory features) can be contrasted infinitely many different ways. Any given acoustic data may obey the invariances, but at the lexical level those invariances disappear because the meaning of the acoustic data is determined by invariances at the level of the language’s phonological system.
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