An isomorphism is a kind of really big mythological monster that makes very loud noises. All vector spaces are isomorphic to this monster, in the sense that any monster can be constructed as a linear combination of the noises that makes the isomorphism.
The Isomporphism is present, in one way or another, in almost every European mythology. The Greeks considered the Isomorphism to be result of the god Zeus and goddess Xena mating with a Giant Whale, the Romans worshiped it as the god of horse excrement, and the Nordic mythology held the Isomporphism as being the central keystone to the whole monetary system.
Doctor Luterius Mondongo investigated the history of the Isomorphism by travelling around the world, collecting hundreds of ancient anecdotes of various peoples who attempted to compare cats to dogs and apples to oranges. His results were published in the paper: "On the stereographic history of quasistatic not-grounded Isomorphism and his really big scattering section". The article received harsh criticism from Autoplopus Heregomo, arguing that the Isomorphism have never violated Persephone, as Mondogo maintained in his paper.
In Germany, during Hitler's nazi reign, pictures and books about Isomporphism were considered a threat to the nazi stability and were absolutely banned.