John Snow

And that was the official position of the men in charge of public health.

A doctor named John Snow didn't argue with him.

He walked to the general registrar office, asked for the list of the dead, and took that list out into the streets and knocked on doors until he found that nearly all of them had lived a short walk from one water pump on Broad Street.

Now we're going to follow what he did as he applied each of the four steps I'm about to share.

Nobody has handed you an argument to evaluate, so there's nothing to be critical of.

You have to work out what is going on.

Snow's story shows the gap.

Critical thinking applied carefully in 1854 points you straight to the Board of Health, the experts, because they were the credible source making a claim and the credible source, in this case, was wrong.