Recently, several
threads have had some debate about logic, evidence, critical thinking and
skepticism. I wanted to write a post discussing those things, hopefully to
clarify what those things are, why they are important and how to use those
tools.
First, logic, at its
core, is simply a method for how to reason validly, how to draw conclusions
based on a premise. A simple mathematical example is "if A=B then
B=A". In computing, logical operators are used often, AND, NAND, OR, XOR,
etc., are used to evaluate expressions and return results, for example, if
A>0 AND B>0, then return a value of 1, else return 0". If
philosophical logic, an example would be "All trout are fish. All fish
live in the water. Therefore all trout live in the water". Logic is simply
a method for drawing conclusions from facts, a set of premises and other data.
Evidence is that
which we use to for conclusions about things. It can take many forms, physical,
mathematical, etc.. Determining the quality of evidence is a part of critical
thinking.
Critical thinking is
a method for analyzing information using logic, experience, deduction,
induction, the weighting of evidence, the quality of evidence, etc.
Skepticism is about
determining how and when to have reason to believe something to be true or
false, whether or not a thing happened or is true or will happen. For instance,
I've no problem with believing someone when they tell me they had a sandwich for
lunch today. I know sandwiches exists and are common. The evidence I need for
that is next to zero. However, if that person had lunch with me and I watched
her eat a salad, I've direct evidence to the contrary and have reason to
disbelieve them. Were someone to tell me
they have an invisible dragon in their garage, the weight of the claim requires
more evidence than for a claim of having a sandwich and I've no reason to
believe it absent evidence.
All of these are
components of quality thinking. One other component is knowledge. For instance,
if we were discussing why the Hubble telescope can't see the moon rover or flag
left behind on the moon, some knowledge of telescopes and how they work is required
to understand it. If you don't have that knowledge and aren't willing to learn
about how telescopes work, then your opinion on that doesn't carry any weight.
If you haven't bothered to learn about evolution, biology, etc., then your
opinion on the truth of evolution doesn't carry any weight.
However, using logic
and critical thinking, we can determine whether or not claims make sense. For
instance, were someone to make the claim "All fish swim. Penguins swim.
Therefore, penguins are fish.", I can logically pointing out, without specific
knowledge of which fish, penguins, location, etc., that the statement is
logically invalid and the conclusion does not follow from the premise.
Similarly, "All fish swim, trout swim, therefore trout are fish"
reaches the correct conclusion but from the incorrect premise and logic. It's
often called "right for the wrong reasons" or "right by
accident". The conclusion, although correct, is logically invalid.
Critical thinking is
putting all of this together to come to conclusions. It's using experience,
knowledge, logic and evidence to come to a decision. It's realizing when work
is needed to gain education to properly understand a subject. It's using experience
to know when something makes sense (for instance, if someone were to tell me
that my friend who weighs 120 lbs ate 50 lbs of steak in an hour, I don't need
extensive biology knowledge, just experience, to know that isn't true) or
doesn't.
This is not meant to
cover all forms of thinking or to be an exhaustive guide on how to think, but
to provide some basics on quality thinking.