There are basically two ways to compare items:
1. concrete: what you can identify with the five senses (sight, touch, sound, hear, smell)
2. abstract : what you can not identify with the five senses (concepts, functions, ideas, purposes, goals, personality)
The concrete comparison is more superficial, the abstract more complete or in-depth.
We want the more in-depth comparison because we want our learning to be in-depth, or complete.
