“I am a man of fixed and unbending principles, the first of which is to be flexible at all times.”

Proposals Relating to the Education of Youth in Pensilvania (1749), p. 22 http://dewey.library.upenn.edu/sceti/printedbooksNew/index.cfm?textID=franklin_youth&PagePosition=1; the statement relates to the teaching of History as a subject, and the last quoted paragraph concludes with the footnote "†": Public Disputes warm the Imagination, whet the Industry, and strengthen the natural Abilities.
Context: History will also afford frequent Opportunities of showing the Necessity of a Publick Religion, from its Usefulness to the Publick; the Advantage of a Religious Character among private Persons; the Mischiefs of Superstition, &c. and the Excellency of the above all others antient or modern.
History will also give Occasion to expatiate on the advantage of Civil Orders and Constitutions, how men and their properties are protected by joining in Societies and establishing Government; their Industry encouraged and rewarded, Arts invented, and Life made more comfortable: the Advantages of Liberty, Mischiefs of Licentiousness, Benefits arising from good Laws and a due Execution of Justice &c. Thus may the first Principles of sound Politics be fixed in the minds of youth.
On Historical occasions, Questions of Right and Wrong, Justice and Injustice, will naturally arise, and may be put to Youth, which they may debate in Conversation and in Writing. When they ardently desire of Victory, for the Sake of the Praise attending it, they will begin to feel the want, and be sensible of the use of the Use of Logic, or the Art of Reasoning to discover Truth, and of Arguing to defend it, and convince adversaries.

"The Revenge of the Sacred in Secular Culture" (1973)

Source: Words of a Sage : Selected thoughts of African Spir (1937), p. 38 ["… moral consciousness is an innate and intimate revelation of the absolute, which exceed every empirical data..." - see above].

Stone's Case (1796), 25 How. St. Tr. 1423.

Commonly attributed to Spencer, information provided in The Quote Verifier: Who Said What, Where, and When (2006) by Ralph Keyes and The Survival of a Fitting Quotation. (2005) by Michael StGeorge http://anonpress.org/spencer/, indicates the attribution may have originated with the book [w:The_Big_Book_(Alcoholics_Anonymous)|Alcoholics Anonymous]]. It was used exactly as written above in the personal stories section of the first edition in 1939 and in 'Appendix II: Spiritual Experience' of all subsequent editions.
: "Contempt prior to examination" was a phrase used by William Paley, the 18th-century English Christian apologist. In A View of the Evidences of Christianity (1794), he wrote:
::The infidelity of the Gentile world, and that more especially of men of rank and learning in it, is resolved into a principle which, in my judgment, will account for the inefficacy of any argument, or any evidence whatever, viz. contempt prior to examination.
:Paley's characterization of non-believers was later modified and used by other religious authors who uniformly attributed their words to Paley. In Anglo-Israel or, The British Nation: The lost Tribes of Israel (1879), Rev. William H. Poole may have been the first to render the quotation in its more familiar and enduring form:
::There is a principle which is a bar against all information, which is proof against all argument, and which cannot fail to keep a man in everlasting ignorance. This principle is, contempt prior to examination.
:Various authors following Rev. Poole would offer new iterations of the quotation into the early decades of the 20th century. Most of these credited William Paley, but by the early 1930s the first obscure publications to falsely attribute this quote to Spencer emerged. Its usage for decades since as a maxim in Alcoholics Anonymous and the twelve-step recovery community has popularized its erroneous association with Herbert Spencer.
Misattributed

Optimism (1903)
Context: The highest result of education is tolerance. Long ago men fought and died for their faith; but it took ages to teach them the other kind of courage, — the courage to recognize the faiths of their brethren and their rights of conscience. Tolerance is the first principle of community; it is the spirit which conserves the best that all men think.