"How are Psychic, Ghost, Dark, and Fairy types different?"

This is a question of aesthetics and I know that the answers will be subjective. Each of these types have introduced what I consider to be different "mystical" elements, which have shifted between types across generations.For instance, original Psychic used to have most of the mythical qualities that Fairy now occupies. Also, Pokémon based on aliens have been given the Psychic type (Mewtwo, Mew, Lunatone, Solrock, Deoxys, Elgyem, Beheeyem), but so have Fairy types (Clefairy/Clefable).Same could be said about Psychic and Dark. Remember the anime episode where Ash faces Sabrina? It was so dark! Kadabra was terrifying! What roles do the Psychic type play now? Dark has occupied the "evil" aesthetic.Dark is basically what Ghost should have been, what with immunity to Psychic as well as being super effective against it. There isn't any real offensive difference between Dark or Ghost.Ghost types are often mischievous, but so are Fairy types. Tricksters and Pranksters overlap both types.What do you think? What are the "themes" of these four types? How are they similar? How are they unique? via /r/pokemon http://ift.tt/2scXqvN