It’s important for attorneys to have a basic understanding of logic and reasoning. This rule goes over some basic concepts that frequently come up in law.
DEDUCTIVE REASONING
Deductive reasoning is a form of logic where based on certain facts you can conclude other facts exist. In law syllogisms are the most popular form of deductive reasoning.
SYLLOGISTIC REASONING
A syllogism takes a general principle, a specific fact, and applies the fact to the principle to reach a conclusion. The following is an example of a syllogism:
General Principle: All men are mortal;
Specific Fact: Socrates is a man;
Conclusion: Therefore, Socrates is mortal.
Syllogistic reasoning is how many experienced attorneys make their legal arguments.
FORTIORI: IF THE LESSER THEN THE GREATER
Fortiori reasoning is when we infer that if an argument that applies to a lesser, then all the more so it applies to the greater. For example if someone goes to prison for aiding in a murder, then all the more so should the murderer go to prison.
The person who aided in a murder is obviously less culpable than the person who actually committed the murder, so if the less culpable person goes to prison then the more culpable person should go to prison too.
INFERENCES
Inferences are conclusions that can be drawn from the evidence. Inferences are extremely important for understanding the rules of evidence, because they are necessary to lay the foundation to introduce evidence at trial. It is also necessary to prove your case if it is based on circumstantial evidence. It might take more than one piece of evidence to make the inference, and there are several different types of inferences.
Unlikely Coincidences: When two or more highly unlikely events occur, it is possible to draw an inference that would explain the two unlikely events. For example if a man’s wife drowns in the bathtub it could be an accident. However if his second wife also drowns in the bathtub, then it could create an inference it was not an accident.
Likely Events: Inferences can be drawn from likely events. If you put a properly addressed letter in a mailbox, there can be an inference the letter made it to the address, since mail generally makes it to its destination.
Consistent With A Common Plan Or Goal: If someone was engaging in conduct meant to achieve a certain goal, it can be inferred their actions intended to achieve that goal. For example if the legislature drafted a statute to achieve a specific goal, it can be inferred the language in the statute was meant to be interpreted in a way consistent with that goal.
FALLACIES
Sometimes people will engage in defective reasoning. These arguments are called fallacies. The following are examples of fallacies:
Shared Attributes Fallacy: This fallacy occurs when people place something in a group because it has a common attribute with that group. For example dogs have hair, Socrates has hair, therefore Socrates is a dog. Although Socrates shares the common attribute of having hair with dogs he is clearly not a dog.
Assumes Facts: In law this generally occurs when lawyers ask a question that assumes facts that are not true or at least in dispute. For example if a lawyer asks a witness if he has stopped beating his wife. The question assumes that he use to beat his wife at some point in time.
Conclusory Statements: Conclusory statements are statements that arrive at a conclusion without any facts to support the conclusion. For example a cop could say the Defendant was speeding without any evidence of the Defendant's speed or the speed limit. Both of these facts are necessary to establish the Defendant was speeding.
