In order to clarify this, we look at
The following five tumblers will be divided into two classes: full and empty.
It is obvious: tumbler 1 belongs to the class full and tumbler 5 belongs to the class empty.
To which distinguishable unique class do the tumblers 2,
3 and 4 belong? These three tumblers are neither 100%
full nor 100% empty. When we take a crisp decision
then they belong neither to full nor to empty.
Indeed, the following can be noticed:
Or with other words:
In the following, we will find a class that covers all tumblers on the globe.