I began this series began by discussing logic, because good thinking - critical thinking - is a skill one must develop, much like learning to play piano. Learning logic is to the thinker what learning chords and finger placement is to the pianist. Critical thinking can be one of the hardest tasks, for the topics and issues to which critical thinking must be applied are oftentimes the same topics and issues that make us the most emotional; moreover, we are forced to find balance between two seemingly opposing inclinations, as Carl Sagan explains:
"It seems to me what is called for is an exquisite balance between two conflicting needs: the most skeptical scrutiny of all hypotheses that are served up to us and at the same time a great openness to new ideas … If you are only skeptical, then no new ideas make it through to you … On the other hand, if you are open to the point of gullibility and have not an ounce of skeptical sense in you, then you cannot distinguish the useful ideas from the worthless ones."
As we continue on in this series, I must note that, even though it may be important, the path of a critical thinker is often a difficult road. Maybe that's why most people don't bother to attempt it, and choose instead to remain with their comfortable and familiar beliefs.
- Inductive vs. Deductive Arguments
- The Necessity of Logic
Two types of arguments * - inductive and deductive - are perhaps best distinguished this way: a deductive argument is one in which, if the argument is sound, it's impossible for the conclusion to be false, whereas an inductive argument is one in which, if the argument is sound, it's merely improbable for the conclusion to be false. Put another way, a deductive argument deals with possibility, whereas an inductive argument deals with probability. Consider this argument:Premise 1: One becomes a Sith Lord only by utilizing the power of Dark Side of the Force. Premise 2: Benedict is a Sith Lord. __________________ ∴ Benedict utilizes the power of the Dark Side of the Force.
This is a deductive argument because, if the argument is sound - i.e., the argument is valid (has proper form) and all the premises are true - then the conclusion must be true, and it's impossible for the conclusion to be false. Now here's an example of an inductive argument:Premise 1: Sith Lords have only ever used red-bladed lightsabers. Premise 2: Benedict is a Sith Lord. __________________ ∴ Benedict uses a red-bladed lightsaber.
This argument is inductive because, if the argument is sound, then the conclusion is only probably true. After all, Benedict might decide to break tradition and start using a green lightsaber. We can't say for certain that he won't. The best we can say is, since this is how things have been for a certain period of time, it's probable that it won't be much different now with Benedict's lightsaber. An interesting aspect of inductive arguments is that, with each argument, the level of probability won't be the same. The argument that says, "the sun has risen each day for as long as the earth has been orbiting the sun; therefore, the sun will rise again tomorrow," has a much greater probability than the argument that says, "Mr. Jones has gone on his morning walk at 6 AM every day for the past 40 years; therefore, Mr. Jones will go on his walk again tomorrow morning." There are more factors which could render the conclusion false in the latter argument than in the former, thus making the former argument's conclusion more probable. In some cases, an inductive argument might even be completely wrong. For example, If I flip a coin and it lands "heads" seven times in a row, I could make an inductive argument saying the coin will land "heads" again, because that's how it's landed each time in the past. We'll come back to this in more detail when we get to the section on fallacies. All I'll say here is that, while this coin flip argument would technically be inductive, it is definitely not a sound argument. I find it to be better form to admit the probability in the conclusion of an inductive argument. For example, in my argument for Mr. Jones' morning walk, my conclusion would look something like this: "Mr. Jones will probably go on his morning walk tomorrow morning." I may even word it like this: "Mr. Jones will probably go on his morning walk, provided nothing out of the ordinary occurs."[* There's also abductive reasoning, which I'll discuss later.]
I've written about this on my blog before. Perhaps I should have started the series with this section, given that there are people out there who deny the value of logic for several reasons (whether miseducation or religious bias or some other reason). A key defense of logic is that logic cannot be denied without using logic and assuming the rules of logic are applicable. A person can say, "logic is bunk," but as soon as she tries to explain why it's bunk, she's appealing to the rules of logic. Likewise (and some people use this as a way of dismissing logic), one cannot prove that logic is "logical" without using logic to prove it and thus using circular reasoning. They're right, by the way: we can't justify logic without breaking logic's own rules. Still, though we cannot justify using logic without appealing to logic (leading to circular reasoning), the presumption of logic is necessary for us to understand anything at all. If we deny the rules of logic, then we must admit that statements like "there is a god" and "there is not a god" are both true – and false. "Obama is a liberal" and "Obama is not a liberal" are equally true - and equally false. You are reading this article and you are not reading this article. Charles Darwin is dead, and he is alive! And anyone who agrees with this is correct – and incorrect. Talk about senseless propositions! Without logic, there can be no actual communication, and no conveyance of any kind of truth. Logic is the most foundational assumption one can make.