At a time of unprecedented restrictions on the liberty of the individual (in the democracies), one can not, I think do better than to turn to J. S. Mill’s 1859 essay “On Liberty”:

“The object of this Essay is to assert one very simple principle, as entitled to govern absolutely the dealings of society with the individual in the way of compulsion and control, whether the means used be physical force in the form of legal penalties, or the moral coercion of public opinion. That principle is, that the sole end for which mankind are warranted, individually or collectively, in interfering with the liberty of action of any of their number, is self-protection. That the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant. He cannot rightfully be compelled to do or forbear because it will be better for him to do so, because it will make him happier, because, in the opinions of others, to do so would be wise, or even right. These are good reasons for remonstrating with him, or reasoning with him, or persuading him, or entreating him, but not for compelling him, or visiting him with any evil in case he do otherwise. To justify that, the conduct from which it is desired to deter him, must be calculated to produce evil to some one else. The only part of the conduct of any one, for which he is amenable to society, is that which concerns others. In the part which merely concerns himself, his independence is, of right, absolute. Over himself, over his own body and mind, the individual is sovereign.”
(See https://www.econlib.org/library/Mill/mlLbty.html).

It is, of course dangerous to attempt to precisely determine what a 19th-century theorist would think as regards the problems facing us in the 21st century. However, on the basis of “the harm principle” outlined above, I think that one can hazard an educated guess as to what Mill would have thought about the lockdown measures introduced due to the COVID-19 pandemic.

Mill would, I believe have accepted (albeit reluctantly) the necessity of some kind of social distancing measures on the grounds that an individual has no right to infect another person with a disease. I am, however not convinced that he would have advocated compulsory lockdown measures such as social distancing enforced by law. and, given his defense of individual liberty he would, in my view have rigorously opposed measures aimed at preventing members of different households from mixing indoors – for example the ban on couples who are not living together from becoming intimate due to concerns over the Corona virus.

Mill was a Liberal, but his views have influenced liberals (with a small l) in all the major UK political parties. It is my hope that liberals (of every party) will make their views heard so as to ensure that in the natural desire to combat Corona, the rights of individual human beings do not get forgotten.

Kevin