The Path of a Critical Thinker — Part 1

If I had to choose the “If You’re Only Going to Read One Thing on Dead-Logic, Read This” blog entries, my gut would want me to say this series is the one. I’m not sure whether my mind agrees with my gut, but I will say that these next few entries will showcase the critical thinking tips and tools that I’ve learned over the past three decades, and discuss some of the foundational principles I learned from the biggest influences in my life in this area: Mr. John Kruzan, Dr. Herman Stark, and Dr. Gary Burlington. I am indebted to these teachers more than they could know.

 

The Path of a Critical Thinker

• Logic vs. Reason

Many people use the words “logic” and “reason” (or “logical and “rational”) interchangeably, but there is an important distinction. Reason is the mental ability to come to conclusions, draw inferences, make judgments, create arguments, and evaluate arguments. Logic is the science that evaluates arguments.

• Valid vs. Sound

An argument in logic has nothing to do with a verbal fight. An argument, as it occurs in logic, is a group of statements (the premises) intended to provide support or justification for another statement (the conclusion). There are two kinds of arguments: those which support the conclusion and those that don’t. If the goal of a critical thinker is to evaluate arguments, then understanding how to evaluate them is imperative.

Arguments must be assessed by both form and content. Arguments that have correct form or structure are called valid arguments. A valid argument is one in which, if the premises are true, the conclusion must be true. Take for example this classic syllogism:

Premise 1: All men are mortal.
Premise 2: Socrates is a man.
Conclusion: Socrates is mortal.

This argument is valid; that is, the argument has proper structure such that, if the premises are true, then the conclusion must be true as well. If all men are mortal, and if Socrates is a man, then he must be mortal. One can feel how the conclusion flows naturally from the premises:

P1: All X are Y.
P2: P is X.
∴ P is Y.

An argument that lacks proper structure is invalid, even if the premises are true (and even if the conclusion is true). For example:

P1: Polar Bears are white.
P2: Abraham Lincoln is the 16th president of the USA.
∴ Cheetahs run faster than humans.

Each premise is true, and the conclusion is also true, but this argument is invalid because it lacks proper form. There is no logical connection from the premises to the conclusion.

Sound arguments are valid arguments with premises that are all true. All sound arguments are valid, but not all valid arguments are sound. Validity only refers to the structure of the argument. It says nothing of whether an argument actually proves anything. Here’s a valid argument that isn’t sound:

P1: All squids live on the moon.
P2: Mike Pence is a squid.
∴ Mike Pence lives on the moon.

Arguments encountered in the realms of religion, philosophy, and politics will be much more complicated than the examples given here; nevertheless, whether an argument has two premises or 200 premises, the argument is either valid or invalid, sound or unsound.

• Arguments vs. Conclusions 

Here is an absolutely essential point to understand in order to be a successful critical thinker: one can reject an argument because it is invalid or unsound and still agree with the argument’s conclusion. Rejecting an argument is not the same as rejecting the argument’s conclusion. People are more inclined to accept arguments which attempt to prove or justify ideas or beliefs they already support, and become less critical of such arguments in the process. A critical thinker cares about truth, not about towing party lines.