The extremists are as far apart as possible on this and other issues, and they hate each other. Most of the rest of us are trapped in between, but often closer to each other than we realize. For democracy to work as it is supposed to, people must be able to meet those they disagree with and address issues with reason, not violence. The extremists will never come together except to fight. This is why a political environment that is polarized to the extremes is a danger to democracy.

Now, I'm not taking a position on this issue; I'm just pointing out that most people take neither extreme position. Most people think that some but not all abortions are morally permissible, and should be legally permissible as well. Maybe they're wrong, but differences of opinion on this issue are almost always over where on the spectrum from conception to birth to allow legal abortions.

Simple Constructive Dilemma:

Either p or q.

If p then r.

If q then r.

Therefore, r.

For this reason, this fallacy is sometimes called "false" or "bogus" dilemma. However, these names are misleading, since not all instances have the form of a dilemma; some instead take the following, also validating form:

Disjunctive Syllogism:

Either p or q.

Not-p.

Therefore, q.

Usually, the truth-value of premisses is not a question for logic, but for other sciences, or common sense. So, while an argument with a false premiss is unsound, it is usually not considered fallacious5. However, when a disjunctive premiss is false for specifically logical reasons, or when the support for it is based upon a fallacy, then the argument commits the Black-or-White Fallacy.

One such logical error is confusing contrary with contradictory propositions: of two contradictory propositions, exactly one will be true; but of two contrary propositions, at most one will be true, but both may be false. For example:

Contradictories It's hot today. It's not hot today. Contraries It's hot today. It's cold today.

A disjunction whose disjuncts are contradictories is an instance of the Law of Excluded Middle, so it is logically true. For instance, "either it's hot today or it's not hot today." In contrast, a disjunction whose disjuncts are contraries is logically contingent. For example, "either it's hot today or it's cold today." If an arguer confuses the latter with the former in the premiss of an argument, they may commit the Black-or-White Fallacy.