Ignorance is degrading only when found in company with riches. The poor man is restrained by poverty and need: labour occupies his thoughts, and takes the place of knowledge. But rich men who are ignorant live for their lusts only, and are like the beasts of the field, as may be seen every day; and they can also be reproached for not having used wealth and leisure for that which gives them their greatest value. ~ Arthur Schopenhauer
A large segment of the American public is sadly deficient in its knowledge of basic business and economic facts of life. The media, which many people say are their primary sources of their business and economic info, do not appear to be making any significant impact on this ignorance.
Frank Bennack, Jr., CEO of Hearst Corporation in 1984 (source: No Comment!. p. 59. ISBN 0275928209.).
For "ignorance is the mother of devotion," as all the world knows.
Robert Burton, The Anatomy of Melancholy (1621), Part III, Section IV. Memb. 1. Subsect. 2. Phrase used by Dr. Cole, Disputation with the Papists at Westminster, March 31, 1559. Quoted from Cole by Bishop Jewel, Works, Volume III, Part II, p. 1202. Quoted as a "Popish maxim" by Thomas Vincent, Explicatory Catechism, Epistle to the Reader (c. 1622). Said by Jeremy Taylor, To a person newly converted to the Church of England (1657). Same found in New Custome. I. I. A Morality printed 1573. (True devotion).
The truest characters of ignorance
Are vanity, and pride, and annoyance.
To each his suff’rings; all are men,
Condemn’d alike to groan,—
The tender for another’s pain,
Th’ unfeeling for his own.
Yet ah! why should they know their fate,
Since sorrow never comes too late,
And happiness too swiftly flies?
Thought would destroy their paradise.
No more; where ignorance is bliss,
’T is folly to be wise.
Thomas Gray, repr. In Poetical Works, ed. J. Rogers (1953). Ode on a Distant Prospect of Eton College, stanza 10 (written 1742, published 1747). 
A generation which ignores history has no past — and no future.
Softmindedness often invades religion. … Softminded persons have revised the Beautitudes to read "Blessed are the pure in ignorance: for they shall see God." This has led to a widespread belief that there is a conflict between science and religion. But this is not true. There may be a conflict between softminded religionists and toughminded scientists, but not between science and religion. … Science investigates; religion interprets. Science gives man knowledge which is power; religion gives man wisdom which is control. Science deals mainly with facts; religion deals mainly with values. The two are not rivals. They are complementary.
Ignorance is a kind of insanity in the human animal. People who delight in torturing defenseless children or tiny creatures are in reality insane. The terrible thing is that people who are madmen in private may wear a totally bland and innocent expression in public.
People who don't know any better will always be in the dark because the power lies in the hands of men who take good care that ordinary folk don't understand, in the hands, that is, of the government, of the clerical party, of the capitalists.
So oft in theologic wars,
The disputants, I ween,
Rail on in utter ignorance
Of what each other mean,
And prate about an Elephant
Not one of them has seen!
John Godfrey Saxe, "The Blind Men and the Elephant," moral, The Poetical Works of John Godfrey Saxe (1887), p. 112. While Saxe said this was a Hindu fable, the story may be found in The Udna, or The Solemn Utterances of the Buddha, chapter 6, section 4, trans. Dawsonne M. Strong, p. 93–96 (1902).
It is my own peculiarity that I cannot bear ignorance, nor the ignorance of ignoramuses, and even less the ignorance of the informed. Therefore, I decided long ago to converse with the reader on this matter, and to construct before his very eyes—and in his face, if necessary—a different, new reader, one constructed according to my own ideas.
Friedrich Schlegel, “On Incomprehensibility” (1800), J. Schulte-Sasse, trans., Theory as Practice (1997), p. 146.
Ignorance is degrading only when found in company with riches. The poor man is restrained by poverty and need: labour occupies his thoughts, and takes the place of knowledge. But rich men who are ignorant live for their lusts only, and are like the beasts of the field, as may be seen every day; and they can also be reproached for not having used wealth and leisure for that which gives them their greatest value.
Schopenhauer, “On books and reading,” Religion: a dialogue, and other essays, T.B. Saunders, trans. (1910).
O thou monster, Ignorance, how deformed dost thou look!
Don't know what good they hold in their hands until
They've flung it away.
Sophocles, "Ajax", trans. John Moore, in David Grene and Richmond Lattimore, eds., The Complete Greek Tragedies (1959), vol. 2, p. 250. There have been numerous translations of this play by Sophocles, with varying translations of these words, spoken by the character Tecmessa. The translation by George Young, The Dramas of Sophocles, p. 102 (1888) reads, "Men of perverse opinion do not know / The excellence of what is in their hands,/ Till some one dash it from them".
Ignorantia non est argumentum.
Translation: Ignorance is no argument.
Baruch Spinoza, Ethica ordine geometrico demonstrata et in quinque parses distincta, Part 1, Addendum; Amsterdam, 1677.
Originally used to oppose traditional theological views that everything exists and is determined by divine intervention because no other plausible reason or explanation is seen.
There's nothing as safe as ignorance — or as dangerous.
Ignorance served no useful purpose; it changed no fact, it offered no shelter.
Michelle West, Echoes in Assassin Fantastic (ed. Martin H. Greenberg and Alexander Potter, 2001), p. 267
I do not approve of anything that tampers with natural ignorance. Ignorance is like a delicate exotic fruit; touch it and the bloom is gone. The whole theory of modern education is radically unsound. Fortunately in England, at any rate, education produces no effect whatsoever. If it did, it would prove a serious danger to the upper classes, and probably lead to acts of violence in Grosvenor Square.
Oscar Wilde, The Importance of Being Earnest, Act I, spoken by Lady Bracknell (1895).
Hoyt's New Cyclopedia Of Practical Quotations
Quotes reported in Hoyt's New Cyclopedia Of Practical Quotations (1922), p. 385-86.
Causarum ignoratio in re nova mirationem facit.
In extraordinary events ignorance of their causes produces astonishment.
A man may live long, and die at last in ignorance of many truths, which his mind was capable of knowing, and that with certainty.
John Locke, Human Understanding, Book I, Chapter II.
The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new dark age.
Tacitus, Agricola, XXX. Quoting Galgacus, the British leader, to his subjects before the battle of the Grampian Hills. Ritter says the sentence may be a "marginal gloss" and brackets it. Anticipated by Thucydides, Speech of Nicias, VI. 11. 4.
Homine imperito nunquam quidquid injustius,
Qui nisi quod ipse facit nihil rectum putat.
Nothing can be more unjust than the ignorant man, who thinks that nothing is well done by himself.