Now that we've ruled out rational explanations for any paranormal occurrences, eliminated external influences, and identified the things most commonly mistaken for the paranormal, what we're left with is possible evidence of the paranormal.

In order to prove that this evidence really represents paranormal activity, you'll need to make sure it is measurable empirical evidence. This is data where a quantitative change can actually be observed. For example, a measurable or observable physical movement or an increase or decrease in atmospheric conditions

Empirical evidence wouldn't include any evidence that is subjective, such as the use of Ouija boards or other communications, although we will look at how this type of subjective evidence is useful and can be validated later.

In the next few lessons, we'll look at a few techniques that can be used to collect measurable evidence.