His definition of assimilation in the Third Edition follows:
The process whereby an immigrant community adopts the outward forms and political allegiance of a host community, without necessarily absorbing the majority culture or adopting the majority religion. (Cf. acculturation.) Unassimilated minorities, which define their allegiance either in contrast to, or in opposition to, the allegiance of the majority, constitute a potential threat to social and political stability, as recent events have amply demonstrated. The received view in Europe is that assimilation is therefore necessary if immigration is to be acceptable. Note, however, that anybody who said as much 20 or even ten years ago risked the charge of racism. That peculiar fact needs an explanation; so far none has been provided.