I'm optimistic about the sustainability of materil progress, but since I'm known for that, I'll refrain. Instead I want to express optimism about world politics, especially about world peace.
World peace is what we have. There are only minor wars and no present
prospect of a major war threatening western civilization and its present extensions to the actually developing countries. Only Africa and the Arab world are in bad shape.
Contrast this with the time between 1914 and 1989, when there were
serious attempts at world domination accompanied by at least three
Admittedly something bad and surprising could happen. 100 years ago,
in 1907, no-one predicted such troubles as happened. Even in April 1914, Bertrand Russell could write:
"To us, to whom safety has become monotony, to whom the primeval savageries of nature are so remote as to become a mere pleasing condiment to our ordered routine, the world of dreams is very different from what it was amid the wars of Guelf and Ghibelline. Hence William James's protest against what he calls the "block universe" of the classical tradition; hence Nietsche's worship of
force; hence the verbal bloodthirstiness of many quiet literary men. The barbaric substratum of human nature, unsatisfied in action, finds an outlet in imagination. In philosophy, as elsewhere, this tendency is visible; and it is this, rather than formal argument, that has thrust aside the classical tradition for a philosophy which fancies itself more virile and more vital."
As for Arab jihadism, I think they'll get over it as soon as a new generation matures to oppose their parents' slogans. If not
Whatever happens we have got
The Maxim Gun, and they have not.
— Hilaire Belloc, 1898, The Modern Traveller, part 6.
It is important that the political causes of the 20th century disasters, virulent and militaristic nationalism accompanied by letting one man take power, do not exist in major countries today. Communism is dead as a motivator of violence. The green movement is accompanied by occasional minor violence, but a green Hitler or Stalin seems unnlikely.
Still, it's hard to predict 100 years ahead. As Stephen Hawking advocates, humanity would be safer if it expanded beyond the earth.