Next step in gravity and cosmology: fundamental theory or data-driven
  models?
  We comment on the difference between bottom-up (i.e., data-driven, ad hoc)
and top-down (i.e., derived from a fundamental theory of gravitational
interactions) cosmological models, their respective status, predictive power
and viability. We fuel the debate on whether present and future research on
theoretical models of inflation, dark energy and gravitational waves should
concentrate on bottom-up models such as $f(R)$, Horndeski or DHOST theories or
on cosmological models of quantum gravity.
