While I sympathize with some of the points that Moshe made — namely, that if we start boycotting entire countries or states because some aspects of their policies are not “liberal” enough, we will have a serious problem finding a place to hold conferences in, perhaps only Sweden ? — I overall still respectfully disagree and think he confuses two issues.

The first issue is, to put it bluntly: should the scientific community boycott countries whose policies are deemed hostile to human rights? Where should the threshold be? Moshe points out, correctly, that we hold conferences in the People's Republic of China, a country that does not operate according to the principles of liberal Western democracies... The ethical questions are complex: should scientific societies take positions on political issues that fall outside of their narrow remiss? Is the fact that the immigration status of scientists relevant to the development of science sufficient to justify such involvement? How about countries or states that discriminate against LGBT, which affect LGBT scientists? And how about countries whose policies are hostile to the scientific process itself — does not the current US administration show signs of attempting to silence scientists on “politically sensitive” topics such as climate change?

Not only are there ethical questions, but there are pragmatic questions as well. What are the aims of a boycott? Is a boycott likely to influence the policies of the targeted country? I myself doubt that a man such as Donald Trump and his voters give one dime about the opinions of foreign scientists, whom they can easily dismiss as pretentious loser pinko commies living in a ivory tower in overrated countries.

These questions are complicated, and I am probably not well equipped to address them. However, these were not those I was discussing; which brings me to the second issue.

The second issue is far more down-to-earth: in very practical terms, should we (the international scientific community) continue to schedule conferences in the United States, knowing that the visa and entry policies of that country under the Trump administration are likely to be brutal, haphazard, ill-prepared and even gratuitously discriminatory?

This is a very concrete question. In our laboratories, we have many PhD students and faculty coming from countries such as Algeria. Imagine we submit an article to a conference, get it accepted, buy plane tickets, and, on a whim of Donald Trump, is denied boarding. Alternatively, the student boards the plane and gets turned away on arrival to the US (which may be worse, because, if I recall correctly, on further entry to the US he or she will be asked whether he or she has been turned away previously, so it may leave a permanent stain).

This is not only a question of a missed scientific conference — after all, this happens for many other reasons, including illnesses or transportation issues — though one should not forget that in times of shrunk budgets, wasting registration fees, airplane ticket and hotel fees is very unpleasant. This is also a question of the impressions of scientific work and of Western societies that we wish to convey to our students. Should we teach them that they will be permanently regarded as suspects?

Again, I am asking very concrete questions. Conferences are planned well in advance; thus we are discussing right now what happens in 2018. Of course, at this stage, we cannot know whether the Trump administration will continue as it started; things are so wild! However, it is our responsibility to play it safe. We need predictability. We're not talking lofty politics, but decisions with very concrete consequences.

A final word. Moshe remarked, pointedly :

Democracies by nature are less predictable. Should I boycott France if Le Pen wins? Will she be predictable?

Well, indeed, I think that if we in France elected somebody that acted like Donald Trump regarding entry conditions, I'd understand that our foreign colleagues would suggest conferences be moved elsewhere.