Reasoning, reasoning, reasoning. Defined as the action of thinking about something in a logical, sensible way, which is crucial when regarding the big questions of life. However, if we want to get a grasp of this, then we will have to delve into the full scope of what reasoning implies.
There are many, many types of reasoning, such as deductive reasoning, inductive reasoning, abductive reasoning, analogical reasoning, and more. This would be too much to tackle in a single blog, so I will make different blogs about the different types and go a little bit more in-depth into each one.
Now, let’s begin by looking at deductive reasoning.
Deductive Reasoning
In deductive reasoning, general principles are applied to specific cases to make judgments about them. To make your argument, you use premises, which are the base of your conclusion and can be as simple as “The Sky is gray”.
If the premises of your argument are true, then this guarantees the truth of your conclusion. For example, you may know that all dogs have tails, and your teacher’s pet is a dog. Therefore, you conclude that your teacher’s pet has a tail. Without realizing it, you are using a syllogism, which logicians have used since Aristotle and can be understood as a way of arranging the logical parts of an argument. The syllogism that you are using is the following:
- Major premise: All dogs have tails
- Minor premise: My teacher’s pet is a dog
- Conclusion: My teacher’s pet has a tail.
The major premise is a general claim about dogs, and then the minor premise identifies a specific thing- your teacher’s pet- as part of that group. Then it concludes by noting that what is true about the group must be true about this specific thing. Syllogisms take the following form: All A’s are B’s and All C’s are A’s. Therefore, all C’s are B’s. (Syllogisms can also take a negative form: A’s are not B’s. C is an A. Therefore C is not a B).
Now, when looking at syllogisms it is important to consider that there is a difference between validity and truth.
- Validity: The argument has a sound basis in logic and is reasonable. If the argument makes conclusions that do not correspond with the premises, then the syllogism can be easily refuted as invalid (ex. “All dogs have tails, and my teacher’s pet is a dog, therefore my teacher’s pet has eyes).
- Truth: The argument is in accordance with fact or reality. A syllogism can be valid but not necessarily true (ex. All dogs are purple, and my teacher’s pet is a dog, so my teacher’s pet is purple).
Sometimes, it can be difficult to detect a deductive argument and its syllogism because people take shortcuts to get their claims. For instance, they may state one premise and implicitly state the other: My teacher’s pet is a dog, so it must have a tail! In this case, the major premise is made by implication.
It is also important to note that premises are rarely stated with absolute certainty because the conclusions you make may be wrong despite your two premises being generally right. With the example in which I conclude that my teacher’s pet has a tail, what if my teacher’s pet is a corgi, a dog breed that does not have a tail? In real life, I would usually express that claim as “Most dogs have tails so my teacher’s dog probably has one”.
Deductive reasoning that is abbreviated or based on claims about their probability is called “enthymeme”. Enthememes help us communicate more effectively and make judgments based on evidence. However, be warned! As you have probably noticed, enthymemes enable people to omit the least certain part of the premises, concealing the weakness of the claim. For this reason, when you hear a deductive claim, stop and think about the underlying assumptions. If a dog breed does not have a tail and I say “My teacher’s pet is a dog, so it must have a tail” then I have left the premise that is based on probability unspoken, hiding the fact that the claim may not be true.
In the next article post, we will look into the topics for deductive reasoning and some of the fallacies that might result when making a deductive argument.