[To a man expecting a scientific proof of the impossibility of flying saucers] I might have said to him: “Listen, I mean that from my knowledge of the world that I see around me, I think that it is much more likely that the reports of flying saucers are the results of the known irrational characteristics of terrestrial intelligence than of the unknown rational efforts of extra-terrestrial intelligence.” It is just more likely, that is all. It is a good guess. And we always try to guess the most likely explanation, keeping in the back of the mind the fact that if it does not work we must discuss the other possibilities.

A thing is either alive or it isn’t; there is nothing that is almost alive. There is but the remotest possibility of the origin of life by spontaneous generation, and every likelihood that Arrhenius is right when he dares to claim that life is a cosmic phenomenon, something that drifts between the spheres, like light, and like light transiently descends upon those fit to receive it.

As a doctor, as a man of science, I can tell you there is no such thing as curses Everything just happens as a question of probability. The statistical likelihood of a specific event.

Expertise in one field does not carry over into other fields. But experts often think so. The narrower their field of knowledge the more likely they are to think so.

Frequently, I have been asked if an experiment I have planned is pure or applied science; to me it is more important to know if the experiment will yield new and probably enduring knowledge about nature. If it is likely to yield such knowledge, it is, in my opinion, good fundamental research; and this is more important than whether the motivation is purely aesthetic satisfaction on the part of the experimenter on the one hand or the improvement of the stability of a high-power transistor on the other.

In all likelihood, it is the local conditions of society, which determine the form of the disease, and we can so far think of it as a fairly general result, that the simplest form is the more common, the more paltry and unbalanced the food, and the worse the dwellings are.

The present state of the system of nature is evidently a consequence of what it was in the preceding moment, and if we conceive of an intelligence that at a given instant comprehends all the relations of the entities of this universe, it could state the respective position, motions, and general affects of all these entities at any time in the past or future. Physical astronomy, the branch of knowledge that does the greatest honor to the human mind, gives us an idea, albeit imperfect, of what such an intelligence would be. The simplicity of the law by which the celestial bodies move, and the relations of their masses and distances, permit analysis to follow their motions up to a certain point; and in order to determine the state of the system of these great bodies in past or future centuries, it suffices for the mathematician that their position and their velocity be given by observation for any moment in time. Man owes that advantage to the power of the instrument he employs, and to the small number of relations that it embraces in its calculations. But ignorance of the different causes involved in the production of events, as well as their complexity, taken together with the imperfection of analysis, prevents our reaching the same certainty about the vast majority of phenomena. Thus there are things that are uncertain for us, things more or less probable, and we seek to compensate for the impossibility of knowing them by determining their different degrees of likelihood. So it was that we owe to the weakness of the human mind one of the most delicate and ingenious of mathematical theories, the science of chance or probability.

The recurrence of a phenomenon like Edison is not very likely. The profound change of conditions and the ever increasing necessity of theoretical training would seem to make it impossible. He will occupy a unique and exalted position in the history of his native land, which might well be proud of his great genius and undying achievements in the interest of humanity.

The strongest cause in the generation of diseases is the predisposition of the body which is likely to fall ill.

We fooled ourselves into thinking this thing wouldn’t crash. When I was in astronaut training I asked, “what is the likelihood of another accident?” The answer I got was: one in 10,000, with an asterisk. The asterisk meant, “we don’t know.”