A sane judgement requires a careful distinction between two kind of ideas that we have on the external world. They are named observations and inferences.
Observations result from personal perception.
To observe something, we must see, hear, feel, taste . The inferences are decisions on the meanings of our observations. These two types of ideas are essential to our own functionning, but when we confuse inferences and observations, we have some troubles. Carefully read the following story, assuming that all it says is accurate. But, at times, they are deliberately vague.