You're absolutely right. And that is precisely their charm to a mature mind.

When I described the titles as "unthinkable to the modern sensibility" I was dodging mention of such topics as the "Physiognomy of the Pygmy peoples" or "Universal suffrage by all necessary means" - which are basically books on racism and terrorism, for example as espoused in the works of Emma Goldman.

Old books are dangerous. Ideas are dangerous. Our modern ideas no less so, and to claim otherwise is a "parochialism of the present".

But ones understanding of the world will be much richer, and intellect fortified by at least knowing of these books and ideas, Otherwise we may as well join the ranks of Firemen of Bradbury's 451 brigade.