You have a pet dog and a pet cat. Maybe they don’t get along very well together. You think of the cat as having a certain set of qualities, it looks and behaves a certain way and the dog looks and behaves in a certain way quite distinct to the cat’s. The dog poops outside, the cat poops inside. The dog bothers company wanting petted and scratched, the cat runs and hides from company. The more differences you look for, find, and think about, the more different your two pets seem. Then one day you come home and find the dog asleep with the cat curled up against the dog also asleep. They are comforting each other with warmth. You see that and think, Aha! My cat and my dog are both the same in the sense that they are both my pets that I love.
They are still separate as cat and dog, but your perception of them has transcended that distinction and you now relate to their sameness in a profound way. Even if they don’t get along, as well, at some later time, that sight of them curled together asleep will remain your primary experience of your two beloved pets.
Brief illustration included in my work-in-progress Joseph Campbell book I’m writing as a Christmas present for my sisters’ kids. Posting bits as I go. There are more under the Joseph Campbell category tag and more will be coming.