“The generals aren't doing so well right now. Now, I have a feeling it may be Obama's fault. But if you look at ISIS… General MacArthur and General Patton, they're spinning in their graves. The generals certainly aren't doing very well right now.”

from a transcript of the video interview "Understanding Relativity," published at webofstories.com

Answer to question about whether he's mused about Armageddon. Interview http://www.reagan.utexas.edu/archives/speeches/1983/120683c.htm for People magazine (12 June 1983)
1980s, First term of office (1981–1985)

In Muncie, Indiana on Saturday, April 12, 2008 clarifying the remarks he had made in his San Francisco speech the previous Sunday. Transcript of Obama's Remarks in Muncie, Indiana (12 April 2008) http://thepage.time.com/transcript-of-obamas-remarks-in-muncie-indiana/
2008
Context: Lately there has been a little typical sort of political flare up because I said something that everybody knows is true which is that there are a whole bunch of folks in small towns in Pennsylvania, in towns right here in Indiana, in my hometown in Illinois who are bitter. They are angry. They feel like they have been left behind. They feel like nobody is paying attention to what they're going through. So I said well you know when you're bitter you turn to what you can count on. So people they vote about guns, or they take comfort from their faith and their family and their community. And they get mad about illegal immigrants who are coming over to this country or they get frustrated about you know how things are changing. That's a natural response. And now I didn't say it as well as I should have because you know the truth is is that these traditions that are passed on from generation to generation those are important. That's what sustains us. But what is absolutely true is that people don't feel like they are being listened to. And so they pray and they count on each other and they count on their families. You know this in your own lives and what we need is a government that is actually paying attention. Government that is fighting for working people day in and day out making sure that we are trying to allow them to live out the American dream. And that's what this campaign is about. We've got to get past the divisions. We've got to get past the distractions of our politics and fight for each other. That is why I am running for president of the United States. And I think we've got an opportunity to bring about that change right here and right now. But I'm gonna need your help Indiana. I'm gonna need your help.

Alphabet Juice (2008), p. 17.

2010s, Europe at the Edge of the Abyss (2016)

Harvard Graduation Speech (2017)

"Why True Love Waits," talk in Ouray, CO (2007-06-15)

Original in French: Comprenez-vous maintenant le lien qui existe entre la question des générations spontanées et ces grands problèmes que j'ai énumérés en commençant? Mais, messieurs, dans un pareil sujet, assez de poésie comme cela, assez de fantaisie et de solutions instinctives; il est temps que la science, la vraie méthode reprenne ses droits et les exerce. Il n'y a ici ni religion, ni philosophie, ni athéisme, ni matérialisme, ni spiritualisme qui tienne. Je pourrais même ajouter : Comme savant, peu m'importe. C'est une question de fait; je l'ai abordée sans idée préconçue, aussi prêt à déclarer, si l'expérience m'en avait imposé l'aveu, qu'il existe des générations spontanées, que je suis persuadé aujourd'hui que ceux qui les affirment ont un bandeau sur les veux.
Also found in Histoire du développement de la biologie, Volume 3, by Hendrik Cornelius Dirk de Wit (1994), PPUR presses polytechniques, p. 393
Soirées scientifiques de la Sorbonne (1864)
Context: Do you understand now the relationship between the question of spontaneous generation and the major problems that I listed in the beginning? But, gentlemen, in such a subject, rather than as poetry, pretty fancy and instinctive solutions, it is time for science, the true method resumes its duties and exercise. Here, it takes no religion, no philosophy, no atheism, no materialism, no spiritualism. I might even add: as a scholar, I do not mind. It is a matter of fact; I approached without a preconceived idea, too ready to declare, if the experiment had imposed upon me the confession, that there was a spontaneous generation, of which I am convinced today that those who assure it are blindfolded.

Wars I Have Seen (1945)