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Published online by Cambridge University Press: 10 December 2025
Goldstern showed in [7] that the union of a real-parametrized, monotone family of Lebesgue measure zero sets has also Lebesgue measure zero, provided that the sets are uniformly
$\boldsymbol {\Sigma }^1_1$. Our aim is to study to what extent we can drop the
$\boldsymbol {\Sigma }^1_1$ assumption. We show that Goldstern’s principle for the pointclass
$\boldsymbol {\Pi }^1_1$ holds. We show that Goldstern’s principle for the pointclass of all subsets is consistent with
$\mathsf {ZFC}$ and show its negation follows from
$\mathsf {CH}$. Also we prove that Goldstern’s principle for the pointclass of all subsets holds both under
$\mathsf {ZF} + \mathsf {AD}$ and in Solovay models.