If he stops to think, he would know that it was just a shadow. But the dog was not thinking anything, and instead dropped the bone he was carrying and jumped into the river. The greedy dog finally struggled to swim to the edge of the river. When he safely reached the bank, he just stood pensive and sad because the bone it carries even disappear, he later regretted what had happened and realized how stupid he was.
So we can Model learning from the fabled dog and its shadow are Do we have a greedy nature as it can be bad.