Round and round we go. From Ben Southwold:
(a) restricting migration restricts extremely important rights, like the freedom to take a job you are offered and the freedom to offer a job to a desired applicant, (b) when we curtail these sorts of freedoms we need to have a preponderance of evidence that the costs are very high, (c) the economic evidence says immigration is pretty good for the recipient country, very good for the source country, and amazingly good for the migrant themselves, (d) the magnitude of the social/cultural impact (i.e. the effect of migrants on our institutions, customs, etc.) is unclear, (e) therefore, we ought to have open borders (or something very close to open borders).
Ben Six responds:
To my mind, the burden of proof lies with advocates of radical change. One requires a large body of evidence to justify a course of action that would significantly and permanently change a stable and somewhat civilised nation.
I disagree, of course. Similar arguments were made in the antebellum south. Slavery was a well established system. Destroying it, argued white slave owners, could perhaps be justified but a lot of evidence would be required to prove such a radical change was worthwhile.
This argument sounds evil and ridiculous now, but were they so wrong? Ex ante they had the weight of tradition on their side, ex post blacks in the south continued suffering intensely under sharecropping and Jim Crow, without much of a material improvement over their pre-emancipation condition.
How you feel about these arguments will depend on how you feel about slavery. Under what conditions does the burden of proof fall on the radical? When it comes to slavery I don’t think the burden falls on the revolutionary. I think a similar logic applies to immigration restrictions.