2. The only things included in these formal guides are:
A. Those things so generally recognized as being true it is believed by the authors there is no need to cite a source -- Unfortunately, as Buddha said, "Just because a thing is generally believed to be true does not mean it is true. Therefore do not accept if for that reason alone." (paraphrased.)
B. Those things established through research, polls and statistics.
Research is often over turned when some new factor is discovered that influences it, sometimes research supports more than one point of view, sometimes research is faulty, and sometimes, as in the cigarette debate, outright purchased. Therefore while research is indicative it should never be accepted without reservations.
Polls are unreliable unless you know the questions that were asked. For instance I can prove fully 80% of the hearing people in my town hate Deaf people by asking them "How many Deaf people do you know you like?" Since at least 80% of the hearing people in town have never knowingly interacted with a Deaf person they will answer "none." But if I ask those same people "Do you dislike Deaf people," those same people will answer "No." Proving my town to be one of the most Deaf friendly in the nation.
And you have to love statistics! How a statistic is presented almost guarantees the reaction you will receive.
One of my granddaughters came up to me scared out of her wits after listening to some news person say "How dangerous the world is today." She quoted "And Boompa there are 30 to 40 serial killers loose in the U.S. at any given time. It could be your neighbor."
True, it could be, but -- There are 350,000,000 people in the U.S.A. which means one in every 100,000,000 people is a serial killer. The percentage may have never changed throughout history.
Which means you are 3 times more likely to win the California lottery than you are to meet a serial killer.
C. Those things that are backed by authority. Unfortunately if you know how to do research you can find some authority somewhere to back up almost any opinion you want to present -- And if you want to sell your textbook you will find the authorities who will back up the opinion the purchasers of your textbook will want to read. So in this case you are learning the opinions approved of by those who buy the textbooks for the school system that uses them.
D. By and large textbooks are designed to teach you things to be memorized during class and recalled during test taking. Thus a minimum of complexity or controversy is included. Textbooks are not set up to have your knowledge tested through essay questions, which is the best way to test your comprehension of a subject, but by multiple choice testing, which is the most convenient way to test your comprehension of a subject.
Thus textbooks are more akin to indoctrination tools than comprehension tools.
E. Textbooks tend to obfuscate rather than clarify. Often things are approached in the hardest possible way to learn -- And time is spent learning jargon so you can discuss relatively simple subjects with a vocabulary that makes it sound exceedingly important.
Thus you read: "The inherent diversification among the various Deaf communities indigenous to the United States is greater than previously estimated." instead of reading, "Every Deaf club has its own personality."
I could go on but 5 points should be enough to satisfy Eris.
So let us say you have no access to D/deaf people so you can expand your experience -- What do you do?
AllDeaf is a good choice. Harris Communications ->
Harris Communications - products for deaf, hard of hearing, hearing impaired, hearing loss, and sign language. Harris Communications - Vibrating Alarm Clocks, Loud Telephones and Signalers is excellent -- Look for the label "Deaf Author" when choosing a book. Another wonderful place is
OIC Movies - American Sign Language (ASL) Deaf Videos. If you are not good at ASL pay your $59 yearly subscription fee and it will be subtitled for the signing impaired. Fantastic deal.
Another thing to do, on ANY subject, when using a textbook, is to use the textbook as a starting point – Not a final word as at least one person does on this forum. You do this by checking every statement on the internet. Try rephrasing the text book in simple, or simply different language. Look for differing opinions, see which ones tend to fit your world view and which ones don't. After a while you will get a feel for the subject you cannot get any other way.
Just remember, when it comes test time, give the teachers the answers they want – Unless you want to be like I was in school, give the kids around you the “right” answers so they could pass while I wrote down the “true” answers and proudly walked away with my straight “F” average.