"Necessity is the mother of invention." Aesop's insight continues to be true in the various facets of life — both personal and societal. For immigration and immigration policy, too, necessity is the mother of invention. Actually, it is perhaps more accurate to say, in the case of immigration, that "necessity is the mother of realism". Necessity can be a reality check — much as we see in the Biblical story of the prodigal son, whose hunger (necessity) prompts his "coming to his senses" (Luke 15:17).
Our neighbors to the north, known for their peaceful juxtaposition and quiet reserve, and also known as a nation that proactively promotes multiculturalism, because of necessity are re-evaluating their approach to and standards for immigration. An interesting recent Wall Street Journal article highlights this.