Ideas are created by integrating previous ideas and sensory input.
Due to this dependency of ideas on previous ideas or sensory input, we know that knowledge is hierarchical.
Every higher level concept is based on a lower level information.
At the root of all of this, of course, is perception.
The very first concepts are derived directly from perceptions, via reason.
Future concepts can then use the first concepts as part of their base, but the foundation is always there.
The understanding of how a particular concept is tied to lower level concepts or sensory input is useful.
It allows a more explicit understanding of the concept.
Without knowledge of the hierarchy, one is left with only a vague notion of the meaning of a term.
Since we learn some concepts from others, we may only have an ambiguous idea of what the term means.
This "notion" is not really a concept.
It is a place holder for a concept.
One can understand enough about the concept to differentiate it from other concepts one is aware of, while still
not grasping exactly what it refers to.
Without an understanding of one's hierarchy of knowledge, it is possible to lose sight of
some features of a concept.
This seems to happen frequently in philosophy.
This is how people can claim that they don't exist, or that reality doesn't.
Since it is possible to ignore the foundation of an idea, it is possible to use it in a way
that specifically contradicts the foundation.
An example of this nonsense is people 'proving' that logic
doesn't exist, when the concept 'proof' is derived from the concept logic.
(This page mirrored from Importance of Philosophy.com)