The relevant stages were (1) whether the classification was founded on an intelligible differentia; and (2) whether the differentia had a rational relation to the object sought to be achieved by the law in question.
The latter permits the State to classify persons for legitimate purposes, provided there is a reasonable basis for the same, meaning that the classification is required to be non-arbitrary, based on a method of intelligible differentiation among those sought to be classified, as well as have a rational relation to the object sought to be achieved by the classification.
This dualism (non-rational-disorderly-bad vs. rational-orderly-good) pervades also the sensible or physical world, since the human soul, being derivative from the world soul, has a rational and a non-rational aspect too, as the Republic proposes.
"The challenged regulations bear a rational relation to legitimate penological interests," Justice Anthony M. Kennedy wrote for seven members of the court.
Both over- and under-inclusiveness are currently tolerated in Singapore under the rational nexus test, as a classification can still bear a rational relation to the legislative objective notwithstanding that it embraces more or less persons than its object requires.
In 2003, the US supreme court unanimously decided that visitation restrictions with a "rational relation" to prison management do not violate the constitutional right of association.
We show how to modify the original set of defaults in order to obtain as output a rational relation.
Second, a model needs to be developed, describing a rational relation between the measure and the implementation effort.
(Despite the way he talks, Scotus does not mean here to deny that similarity is a reflexive relation; his view is that reflexivity is a property merely of what the medievals labeled "rational relations," and that the similarity that obtains between two distinct objects is not such a rational relation. The point is not worth dwelling on).
