Politicians, courts and activists invoke the “public interest” at the drop of a hat, the better to marshall it in support of a favored doctrine or project. But consider this:
For the sake of the public interest Plato and Fichte defended the withdrawal of the children from their parents and wanted their education to be entrusted to the body politic. With an appeal to the public interest Plato wanted to abolish marriage and private property as far as the ruling classes of his ideal State were concerned. Aristotle wanted education to be made uniform in ‘the public interest’; on the same ground Rousseau wished to destroy all the particular associations intervening between the State and the individual citizen. Wolff desired the body politic to meddle with everything human and, at least for the Protestant Churches, he wanted the government to fix the confession.
The idea of the ‘salus publica’ was the hidden dynamite under the Humanistic natural law theories of Hugo Grotius and S. Pufendorff. In Chr. Wolff’s doctrine of natural law this idea resulted in a frankly admitted antinomy with his theory of innate natural rights. The slogan of the public interest was the instrument for the destruction of the most firmly established liberties because it lacked any juridical delimitation. The terrible threat of Leviathan is audible in this word as long as it is used in a juridically unlimited sense. The universalistic political theories could conceive of the relation between the State and the non-political societal structures only in the schema of the whole and its parts. This is why they could not delimit the idea of ‘the public interest’.
(“Dooyeweerd 1997–III: pp. 442–443)