Even though [Donald] Trump is reported to not read very much and to have a limited range of experience, he is often certain that he is right and boldly asserts the correctness of his positions.

At one point, for example, [Donald Trump] argued that he knew much more than military leaders about the pursuit and defeat of ISIS. His assuredness of his own correctness seems also rooted in arrogance reflecting his fundamental insecurity. This insecurity and his belief in his own rightness, when combined with his success at making money, leads him to be self-reliant in his decision-making, which could result in his taking risks with threatening or using nuclear weapons.

That so much power over the U.S. nuclear arsenal is placed in the hands of one man - any man - bodes ill for humanity, while completely undermining the war power granted to Congress in the U.S. constitution.

Perhaps the singular positive of [Donald] Trump's desire to improve the deteriorating relations between the U.S. and Russia will lead to achieving progress toward a world free of nuclear weapons.

During the primaries, if another candidate criticized him, [Donald] Trump would respond with even stronger criticism toward his attacker.

Sooner or later there will be a nuclear 9/11 [by Islamic terrorists] in an American city or that of a US ally... A terrorist nuclear attack against an American city could take many forms. A worst case scenario would be the detonation of a nuclear device within a city. Depending upon the size and sophistication of the weapon, it could kill hundreds of thousands or even millions of people.

That the man in question should be Donald Trump, with all his personal flaws, challenges the United States and the world as never before in human history.