“We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation.”

Source: The Production of Security (1849), p. 25

The Structure of the Universe: An Introduction to Cosmology (1949)
Context: The philosophical consequences of the General Theory of Relativity are perhaps more striking than the experimental tests. As Bishop Barnes has reminded us, "The astonishing thing about Einstein's equations is that they appear to have come out of nothing." We have assumed that the laws of nature must be capable of expression in a form which is invariant for all possible transformations of the space-time co-ordinates and also that the geometry of space-time is Riemannian. From this exiguous basis, formulae of gravitation more accurate than those of Newton have been derived. As Barnes points out...

Source: Mathematical Thought from Ancient to Modern Times (1972), p. 441.

Source: The Four Pillars of Investing (2002), Chapter 2, Measuring The Beast, p. 54.

1860s, Letter to James C. Conkling (1863)
Context: But the proclamation, as law, either is valid, or is not valid. If it is not valid, it needs no retraction. If it is valid, it can not be retracted, any more than the dead can be brought to life. Some of you profess to think its retraction would operate favorably for the Union. Why better after the retraction, than before the issue? There was more than a year and a half of trial to suppress the rebellion before the proclamation issued, the last one hundred days of which passed under an explicit notice that it was coming, unless averted by those in revolt, returning to their allegiance. The war has certainly progressed as favorably for us, since the issue of the proclamation as before. I know as fully as one can know the opinions of others, that some of the commanders of our armies in the field who have given us our most important successes, believe the emancipation policy, and the use of colored troops, constitute the heaviest blow yet dealt to the rebellion; and that, at least one of those important successes, could not have been achieved when it was, but for the aid of black soldiers. Among the commanders holding these views are some who have never had any affinity with what is called abolitionism, or with republican party politics; but who hold them purely as military opinions. I submit these opinions as being entitled to some weight against the objections, often urged, that emancipation, and arming the blacks, are unwise as military measures, and were not adopted, as such, in good faith.

Thus writes Blackstone, to whom let all honour be given for having so far outseen the ideas of his time; and, indeed, we may say of our time. A good antidote, this, for those political superstitions which so widely prevail. A good check upon that sentiment of power-worship which still misleads us by magnifying the prerogatives of constitutional governments as it once did those of monarchs. Let men learn that a legislature is not “our God upon earth,” though, by the authority they ascribe to it, and the things they expect from it, they would seem to think it is. Let them learn rather that it is an institution serving a purely temporary purpose, whose power, when not stolen, is at the best borrowed.
Pt. III, Ch. 19 : The Right to Ignore the State, § 2
Social Statics (1851)

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

Source: "Outlines of the Science of Energetics," (1855), p. 121; Second paragraph

Some Men are More Perfect Than Others (1973)