  We argue that accidental approximate scaling symmetries are robust
predictions of weakly coupled string vacua, and show that their interplay with
supersymmetry and other (generalised) internal symmetries underlies the
ubiquitous appearance of no-scale supergravities in low-energy 4D EFTs. We
identify 4 nested types of no-scale supergravities, and show how leading
quantum corrections can break scale invariance while preserving some no-scale
properties (including non-supersymmetric flat directions). We use these ideas
to classify corrections to the low-energy 4D supergravity action in
perturbative 10D string vacua, including both bulk and brane contributions. Our
prediction for the K\"ahler potential at any fixed order in $\alpha'$ and
string loops agrees with all extant calculations. p-form fields play two
important roles: they spawn many (generalised) shift symmetries; and
space-filling 4-forms teach 4D physics about higher-dimensional phenomena like
flux quantisation. We argue that these robust symmetry arguments suffice to
understand obstructions to finding classical de Sitter vacua, and suggest how
to get around them in UV complete models.
