ad hominem (ahd HAW-mih-nem)
From The Latin and liberally translated: against the man
More formally known as Argumentum ad hominem, or an argument against the person and not their thoughts. Argumentum ad hominem is a logical fallacy, in that the argument fails to address the issues presented or to support the point of the speaker uttering the Argumentum ad hominem. There is no doubt that an Argumentum ad hominem can be an effective rhetorical tactic on the part of the speaker because it often appeals to emotions or prejudices of the listener rather than intellect, or is directed against the character of the person rather than the subject under discussion.
There are several common fallacies related to Argumentum ad hominem:
- Argumentum ad hominem must involve abusive or foul language
- it is never appropriate to comment on another persons background or qualifications as this is an Argumentum ad hominem, there are cases in which such comments are ad rem
From The Latin and liberally translated: argument from ignorance
The argument from ignorance is a logical fallacy occurring when one claims that something is true only because it hasn't been proved false, or that something is false only because it has not been proved true. Such "arguments" are irrelevant. This is a central issue in philosophy of science and the core of Karl Popper's arguments that scientists must strive to find evidence that undermines their own claims, assertions, and cherished beliefs. A claim's truth or falsity depends upon supporting or refuting evidence to the claim, not the lack of support or refutation from an opponent of the claim. Unlike the Argumentum ad hominem, arguments from ignorance do not involve claiming that any person is ignorant. The fallacy occurs when reasoning from the lack of knowledge that a position is true to the conclusion that an opposing position is therefore true. Robert Carroll of The Skeptic's Dictionary says that "this fallacy might be better called 'the fallacy from lack of sufficient evidence to the contrary.'" The argument from ignorance, within mental health, most often plays upon wishful thinking. People who want to believe in satanic ritual abuse or the ability of others to realign "energy fields", for example, are more prone to think that the lack of evidence to the contrary of their desired belief is somehow relevant to supporting it - nothing could be farther from scientific thinking!
From The Latin and liberally translated: to the matter at hand
Ad Rem, literally "to the thing", can be translated in various ways but is consistently translated as meaning "pertinent" or "relevant". It is the counter-point to Argumentum ad hominem. In matters where a person has asserted that they are an authority, which they can do in any number of ways but which is done most often by claiming certain degrees, certifications, licenses, or other qualifications which supposedly make them entitled to a "professional" opinion, or in any way, directly or indirectly, implies that their opinion based on who they are or their status is to be taken more seriously then that person's background, credentials, and other qualifications become appropriate for discussion and are ad rem and NOT an Argumentum ad hominem.
"An intentional perversion of truth for the purpose of inducing another in reliance upon it to part with some valuable thing . . . ; a false representation of a matter of fact, whether by words or by conducts, by false or misleading allegations, or by concealment of that which should have been disclosed, which deceived or is intended to deceive another so that he shall act upon it . . ." Black's Legal Dictionary, 4th edition, 1968.
"Health fraud is the promotion, for financial gain, of fraudulent or unproven devices, treatments, services, plans or products (including but not limited to, diets and nutritional supplements) that alter or claim to alter the human condition. Those who promote such medical remedies that do not work or have not been proven to work are called "quacks." The Assembly Republican Task Force on Health Fraud and the elderly, New York State Assembly, June 1986.
"Untrue or misleading information." Webster's Seventh New Collegiate Dictionary, 1972
"To contribute to the growth or prosperity of; to present for public acceptance through advertising and publicity." Webster's New Collegiate Dictionary, 1975.
Michael Shermer, Ph.D., is a noted skeptic and the director of The Skeptic's Society. In his book Why People Believe Weird Things (1997), Shermer defines pseudoscience as "claims presented so that they appear scientific even though  they lack supporting evidence and plausibility" (p. 33). In other words, pseudoscience is literally a "false science."
"Anyone who promotes medical schemes or remedies known to be false, or which are unproven, for a profit." U. S. House of Representatives, 1984.
"Promoting" health products, services or practices of questionable safety, effectiveness or validity for an intended purpose." National Council Against Health Fraud, 1986.