So, how do we distinguish clear, critical, and analytical thinking?
Understanding the role of an ASSUMPTION in language usage may help us to understand.
At the very least, we need to recognize what our assumptions are.
It is for this reason that it can also be said that clear thinking is relative to a common acceptance of assumptions.
For instance, scientists accept that there is a "real" world "out there" beyond our sense data.
If they did not, science as a method of inquiry could not exist.
Certainly they do not have a clear concept of the world beyond their sense data.
For this reason "clear" thinking is most often also an illusion of knowledge.
For instance, if one asks a child to select a yellow pencil from among other colored pencils, the child will with "clear" understanding pick the desired pencil.
In fact, the child is too young to have learned that in the real world of objects, he has the illusion of knowledge that the pencil is in fact yellow.
For the moment, let us clarify that much depends on how the term 'yellow' is defined.
There are at least four definitions that come to mind, ignoring that the term, 'yellow,' is often used to "mean" "cowardly." Yellow means:
      1) The object has a disposition to cause a sensation of yellow,
      2) The object emits a wave length of a particular frequency,
      3) The light reflected from the object causes a particular kind of neuron activity in the brain,
      4) Assuming 3 and 4 are not synonymous, the sense datum, the experience of yellow itself.
If, as in the use of ordinary language, "yellow" means number 4, then the statement, "The pencil is yellow," is false.
To some degree, then, it should become apparent that when one seeks the highest degree of clarity, a critical and analytical examination of language becomes imperative.
Determining the truth-value of the claims we make in human affairs, whether professionally or in "everyday life," requires the same education and training that is needed to determine whether the claim that the pencil is yellow is true.
1997 by Pasqual S. Schievella