This is worth considering in light of the nonsense that is presented as
the evidence that "HIV" exists and causes "AIDS:"

"A logical fallacy may mean nothing more than a fallacy or it may
mean an error in deductive reasoning, i.e., a formal fallacy. In the
latter case, it is a flaw in the structure of a deductive argument as
opposed to an error in the premises. When there is a formal fallacy in
a deductive argument it is said to be invalid. The presence of a
fallacy in a deductive argument does not imply anything about the
argument's premises or its conclusion. Both may actually be true, but
the deductive argument is still invalid because the conclusion does not
follow from the premises. By extension, an argument can have a logical
fallacy even if the argument is not a deductive one; for instance an
inductive argument that incorrectly applies principles of probability
or causality can be said to commit a logical fallacy.

Recognizing fallacies in everyday arguments may be difficult since
arguments are often embedded in rhetorical patterns that obscure the
logical connections between statements. Informal fallacies may also
exploit the emotions or intellectual or psychological weaknesses of the
audience."

Source: http://en.wikipedia.org/wiki/Logical_fallacy

And this, the "theory of argumentation" is also worth reading:

"The key components of argumentation:
Understanding and identifying the presentation of an argument, either
explicit or implied
Identifying the conclusion and the premises from which the conclusion
is derived
Establishing the "Burden of proof" - determining who made the initial
claim and is thus responsible for providing evidence why his/her
position merits acceptance
For the one carrying the "Burden of proof", the defender, to marshal
evidence for his/her position in order to convince or force the
opponent's acceptance. The method by which this is accomplished is
producing valid, sound, and cogent arguments, devoid of weaknesses, and
not easily attacked
For the attacker, to listen and find faulty reasoning in the
opponent's argument, to attack the reasons/premises of the argument,
to provide counterexamples if possible, to identify any logical
fallacies, and to show why a valid conclusion cannot be derived from
the reasons provided for his/her argument."

http://en.wikipedia.org/wiki/Argumentation_theory

Regardless of how one sees it, "HIV/AIDS" is some sort of bogus
construct, impervious to criticism, with advocates "believing" in a
fairy tale-like dogma, and refusing to consider alternative
possibilities (which are never afforded anywhere near the kind of
latitude given to evidence that purportedly supports the "HIV/AIDS"
claim).  For example, have markers of oxidative stress (e.g., TBARS)
been systematically studied in "HIV/AIDS" patients?  Have the
markers used to indicate "HIV/AIDS" been studied in patients with
"chronic diseases" and those elderly who are clearly deteriorating
rapidly?  It makes more sense that a "positive" test result means
that the body is undergoing just such rapid deterioration, rather than
being "attacked" by a "wily, paradoxical, mutating,
mysterious"retrovirus that "goes off" like a "time bomb" many
years after it was neutralized (assuming it exists) and for no reason
whatsoever, and this can be studied using the scientific method, but it
never has.  Instead, the "HIV/AIDS experts" make predictions over
and over again, and over and over again they are wrong.

If one prediction of an alternative notion was demonstrated to be
false, on the other hand, many of these people would be saying, "see,
that proves we are right and you are wrong."  They simply refuse to
apply any scientifically relevant standards to their claims, while
insisting on the most rigorous standards for anyone else's. The
scientific method requires that when predictions are false, the claim
is abandoned or "goes back to the workshop."  Yet with
"HIV/AIDS," it seems that such setbacks only encourage the
"experts" to make even bolder claims and predictions - an
"Emperor's New Clothes" kind of situation.  One usually finds
this sort of attitude in "religious cults," and perhaps that is
what "HIV/AIDS" is now, for all intents and purposes, plus the
toxic "medicines" and missed opportunities to actually help people
whose bodies are in crisis (and many who are just fine and should never
have been told that they are "diseased").

"HIV/AIDS" was constructed by people with a biased,
self-contradictory view of "health" and "disease."  They did
not possess the imaginations to think beyond the "germs cause
disease" dogma they were fed in medical or graduate school.  One way
to think of the "logical fallacy" of the "HIV/AIDS" claim
involves how advocates usually "move the pea around" in their
"HIV/AIDS" shell game.  If you disparage the slop that passes for
"isolation of HIV," they say that it is a "reasonable"
isolation in light of the "strong correlation" between testing
positive and "dying of AIDS" (though taking the "cocktail
drugs" or psycho-social factors are never considered, nor are control
groups studied).  When you examine the "correlations" and suggest
that they are not very good (Gallo, in his own book, makes the point
that other correlations are "almost" as good) and may be stronger
for other factors, they say, "well, HIV has been isolated, so we know
that it is the cause."  It is a circle of deceit, and in some cases,
self-deceit.  Apparently, Gallo was not aware of the amount of
imprecision involved in "epidemiology."  If he were, I doubt he
would have made such a smug-sounding statement, which, at least in
retrospect, looks rather desperate, at best.