"There is another way of looking at this issue. Article 16(4) recognises only one class viz., "backward class of citizens". It does speak separately of Scheduled Castes and Scheduled Tribes, as does Article 15(4). Even so, it is beyond controversy that Scheduled Castes and Scheduled Tribes are also included in the expression "backward class of citizens" and that separate reservations can be provided in their favour. It is a well-accepted phenomenon throughout the country. What is the logic behind it? It is that if Scheduled Tribes, Scheduled Castes and Other Backward Classes are lumped together, O.B.Cs. will take away all the vacancies leaving Scheduled Castes and Scheduled Tribes high and dry. The same logic also warrants categorisation as between more backward and backward. We do not mean to say - we may reiterate - that this should be done. We are only saying that if a State chooses to do it, it is not impermissible in law."