There are a number of logical fallacies that are committed regularly by those who endeavor to defend a position or debate a topic. These errors of logic can be seen especially around election time as political candidates use their whit to try to convince people of the truth of their claims. Being able to discern good arguments from bad arguments is necessary in the quest for truth.This skill is all the more important when wrestling with the big social issues of the day. ie. the debates over abortion or homosexuality.
False Dilemma: A false dilemma is when a person sets up an either or distinction that really isn't one. One example common to the evolution/creation debate might go like this:
Christian: "Evolution has been shown to be impossible, therefore you've got to admit that God created life."
Evolutionist: "That's a false dilemma, if evolution is impossible then why can't I believe that aliens created life on earth?"
Or it could go this way:
Evolutionist: "Since the Bible has been discredited then evolution is obviously the mechanism by which life came to exist"
Christian: "That's a false dilemma! Even IF the Bible were discredited, God could still be the creator of life"
Argument from Ignorance: This is arguing that something not yet proven to be true, must be false or something not proven false must be true. Christians are often accused of this one when we argue that God created life because scientists haven't been able to show how life began. In this situation it's often called a 'God of the gaps' argument because we are arguing for the existence of God based on gaps in current scientific theory. This criticism has merit unless evidence is being put forth that actually does support special creation (such as the irreducible complexity argument). Here's how an exchange might happen:
Creationist: "I know that God created life because science has no idea how new body plans emerged via genetic mutations"
Evolutionist: "Just because science hasn't answered that yet, doesn't prove it's true. That's a God of the gaps argument."
(note: here the creationist's error was concluding creation was proven by science's failure. It would have been fine to criticize evolutionary theory as being incomplete and not worthy of being called 'fact' but going further commits the fallacy in question).This fallacy is really a special case of the false dilemma because it's really saying: "either X is proven or X is false" rather than allowing for X to be true, just not yet proven.
Slippery Slope: This is a logical fallacy that uses if-then logic. This occurs when a person argues through a list of increasingly unlikely events to a logical conclusion. How about an example?
"If evolution isn't taught as fact, then biology classes will be teaching religion. Then it won't be long until we have a theocracy in our country and our freedoms are taken away."
You can find this reasoning everywhere these days in regard to the debate over evolution in biology textbooks. Christians use it too in regard to abortion.
"If we allow abortion, then partial birth abortion, soon they'll allow the killing of babies up until they're brought home from the hospital. Then they'll allow the killing of anyone who's inconvenient."
It's important to note that these statements may be true, they just aren't NECESSARILY true. They might be a valid prediction, but they are a logical fallacy simply because they MIGHT NOT be true. For example, is it automatically true that teaching evolutionary controversy will result in teaching Bible in biology classes? Of course not (although it could possibly happen in some...).
Complex question: This is when two propositions are joined together inappropriately. For example:
"Do you support freedom and the right to bear arms?".
Basically the question is phrased in a way that requires you to either agree or disagree with two separate statements as one unit. An interesting example of this is the old stand-by party joke:
"Hey Jack, yes or no...have you stopped beating your wife?"
Yes implies he used to, and no implies he still does. In effect the question being asked is:
"Did you beat your wife? and do you still beat her?"
You will often see this one in campaign slogans: "Vote for Mr. Jones and save our economy".