“Of the fifty or hundred systems of philosophy that have been advanced at different times of the world's history, perhaps the larger number have been, not so much results of historical evolution, as happy thoughts which have accidently occurred to their authors.”

When the Cathedrals Were White http://books.google.com/books?id=TzwVAAAAMAAJ&q="A+hundred+times+I+have+thought+New+York+is+a+catastrophe+and+fifty+times+it+is+a+beautiful+catastrophe"#search_anchor (1947)
Attributed from posthumous publications

Introduction
A Treatise of Human Nature (1739-40)
Context: Nothing is more usual and more natural for those, who pretend to discover anything new to the world in philosophy and the sciences, than to insinuate the praises of their own systems, by decrying all those, which have been advanced before them. And indeed were they content with lamenting that ignorance, which we still lie under in the most important questions, that can come before the tribunal of human reason, there are few, who have an acquaintance with the sciences, that would not readily agree with them. 'Tis easy for one of judgment and learning, to perceive the weak foundation even of those systems, which have obtained the greatest credit, and have carried their pretensions highest to accurate and profound reasoning. Principles taken upon trust, consequences lamely deduced from them, want of coherence in the parts, and of evidence in the whole, these are every where to be met with in the systems of the most eminent philosophers, and seem to have drawn disgrace upon philosophy itself.

Source: Squaring the Circle (1913), p. 10

A More Sure Word of Prophecy (2 Peter 1:19)

The Limits of Evolution, and Other Essays, Illustrating the Metaphysical Theory of Personal Ideaalism (1905), Appendix B: The System in its Ethical Necessity and its Practical Bearings

Essay Do We Survive Death? (1936)
1930s
Context: It is only when we think abstractly that we have such a high opinion of man. Of men in the concrete, most of us think the vast majority very bad. Civilized states spend more than half their revenue on killing each other's citizens. Consider the long history of the activities inspired by moral fervour: human sacrifices, persecutions of heretics, witch-hunts, pogroms leading up to wholesale extermination by poison gases … Are these abominations, and the ethical doctrines by which they are prompted, really evidence of an intelligent Creator? And can we really wish that the men who practised them should live for ever? The world in which we live can be understood as a result of muddle and accident; but if it is the outcome of a deliberate purpose, the purpose must have been that of a fiend. For my part, I find accident a less painful and more plausible hypothesis.

Source: Debunking Economics - The Naked Emperor Of The Social Sciences (2001), Chapter 14, There Are Alternatives, p. 313

1963, American University speech
Context: Let us reexamine our attitude toward the cold war, remembering that we are not engaged in a debate, seeking to pile up debating points. We are not here distributing blame or pointing the finger of judgment. We must deal with the world as it is, and not as it might have been had the history of the last 18 years been different. We must, therefore, persevere in the search for peace in the hope that constructive changes within the Communist bloc might bring within reach solutions which now seem beyond us. We must conduct our affairs in such a way that it becomes in the Communists' interest to agree on a genuine peace. Above all, while defending our own vital interests, nuclear powers must avert those confrontations which bring an adversary to a choice of either a humiliating retreat or a nuclear war. To adopt that kind of course in the nuclear age would be evidence only of the bankruptcy of our policy — or of a collective death-wish for the world. To secure these ends, America's weapons are nonprovocative, carefully controlled, designed to deter, and capable of selective use. Our military forces are committed to peace and disciplined in self- restraint. Our diplomats are instructed to avoid unnecessary irritants and purely rhetorical hostility. For we can seek a relaxation of tension without relaxing our guard. And, for our part, we do not need to use threats to prove that we are resolute. We do not need to jam foreign broadcasts out of fear our faith will be eroded. We are unwilling to impose our system on any unwilling people — but we are willing and able to engage in peaceful competition with any people on earth.

From Albert Einstein and the Cosmic World Order, by C. Lanczos (Wiley, New York, 1956)
Attributed in posthumous publications, Albert Einstein: A guide for the perplexed (1979)