### Isn’t Logic Great?

Who doesn’t like logic? We idolize Sherlock Holmes’ ability to solve mysteries by “eliminating the impossible.” In arguments with friends, we try to prove we’re right using logic, rather than intuition or emotions. And we especially enjoy pointing out others’ logical fallacies–preferably using latin terms.

Don’t pat yourself on the back just yet. Finding logical fallacies is actually much less impressive than you might think. That’s because in the real world, all arguments violate the principles of formal logic.

Yes, perhaps every logical argument you have ever encountered was flawed.

### Discounting Weak Evidence

One pitfall to avoid is prematurely discounting seemingly weak evidence. Weak evidence can take many forms. It could be evidence that seems very unlikely under all hypotheses. Or it could be evidence that is non-intuitive and doesn’t seem to fit what we consider “conclusive” evidence.

When evaluating evidence, it’s easy to get distracted looking for “irrefutable” evidence (more on that in an upcoming blog post). However, that’s a mistake. What’s really important is the ratio between how likely evidence is under the hypotheses.

### Strength in Numbers

How much does a snowflake weigh? How about a drop of water? If you’ve ever shoveled snow, or picked up a large jug of water, you know that the weight adds up. The same principle holds true with evaluating evidence. When starting an analysis, we often find little hints that slightly support one hypothesis over the other. Many people might think that these clues wouldn’t really have an impact. Or they might assume that a piece of evidence with a significant influence on the hypotheses renders other evidence meaningless.

However, just like snow, those little pieces of evidence can add up. It’s hard to shovel up thousands of snowflakes at a time (even though individually they’re almost weightless). Likewise, enough evidence pointing in the same direction can have a weighty influence (even if each individual “proof” is not that strong independently).