Dear Prof. Chetty:<stuff deleted>
[The] claim that "economics is a science" is not really a valid one or even a correct one. It is more than a semantic difference regarding the word 'science'. The fact that is that one can postulate multiple versions of the future (universes U1, U2, ..., Un out of which universe U1 is the one predicted by any particular economic theory T1) in which the predictions of T1 hold only in U1 but not in U2, ..., Un. The difference between the sciences (say, physics) and economics is that the probability of -only- U1 and -not- U2, ..., Un is very high in the case of physics and not -provably- as high in economics.
Furthermore, economics does not, in almost any scenario worth thinking about, operate in a 'closed system' as it were. 'Closed systems' experiments are possible in certain science experiments.
With reference to your article: the 10-week extension in welfare payments result that you cite cannot be viewed as being part of a 'closed system'.Anand