Comparison.
The third step in conception is that of comparison, in which the qualities of several things are compared or examined for likenesses and differences. We find many qualities in which the several things differ, and a few in which there is a likeness. Classes are formed from resemblances or likenesses, while individuals are separated from apparent classes by detection of differences. Finally, it is found that separate things, while having many points of difference which indicate their individuality, nevertheless have a few points of likeness which indicate that they belong to the same general family or class. The detection of likenesses and differences in the qualities of various things is an important mental process. Many of the higher thought processes depend largely upon the ability to compare things properly. The development of attention and perception tends to develop the power of comparison.