Introduction to Logic

Posted by admin at April 16, 2020

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WhatIsLogic - Introduction to Logic

we’ll look at what logic is and the basic structure of logical analysis. In subsequent modules, we’ll dig deeper into how to construct and analyze arguments and apply logical arguments to critical thinking.

What is Logic?

Put simply, formal logic is a system of the rules of right reasoning. Logic helps us determine when an argument has the right form and when it doesn’t. Sometimes when students hear the phrase, “right reasoning” they complain, “But who gets to determine what is right and wrong? Wasn’t logic just invented by some old, dead guys? Why do they get to tell us what is right and wrong in the way we think?” These are very good questions!

First, by using the term “right,” logicians don’t mean that logic tells us what to think. Logic doesn’t tell you to think like a conservative or progressive, or like a socialist or a capitalist, or even an Apple fan or Microsoft fan. These ideas make up the content of your thoughts. Logic deals primarily with the structure of our thinking. Just like you can’t make 2+2 equal to 47 no matter how hard you try, there are certain relationships ideas should be in relative to each other and logic helps us figure out what those relationships should be.

Second, like mathematics, logic wasn’t invented but discovered. Logicians like Aristotle or Ada Lovelace examined relationships between ideas and terms and discovered which ones worked and which ones didn’t and created rules for the relationships that worked. These rules became the system of formal logic.

The First Logician

While its certainly true that humans were using logical thinking well before the Greeks and even formalized some of the rules, the first formal Western logician is widely considered to be Aristotle (died in 322 BCE). We’ll see later that Aristotle’s teacher Plato, and Plato’s teacher Socrates also contributed to the system Aristotle developed. But Aristotle was the first person to systematize the rules that made up formal logic.

The “Big Three” Greek philosophers were Socrates, Plato, and Aristotle. Socrates taught Plato and Aristotle was Plato’s student. One way to remember the order of these thinkers is to take the first letter of their names and put them in reverse alphabetical order: S comes last in the alphabet so Socrates comes first, P is in the middle, so Plato is next, and A comes first in the alphabet so Aristotle is last in the lineup.

The Science of Logic

Logic, then, provides rules for properly ordered thinking and logical analysis is the science that applies those rules to our thinking. More specifically, logic helps us analyze arguments. We’ll talk more about arguments in a bit but for now let’s introduce the following terms in order to better describe what logic is.

  1. Logic is the study of the rules of properly ordered thinking. The rules describe the correct ways ideas should relate to one another.
  2. Logic also studies truth values — the role truth plays in correct reasoning
  3. The rules of logic make up arguments that are used to convey the truth value of ideas
  4. Logic also studies incorrect reasoning called fallacies


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