Van Vogt's fiction nearly always criticizes society to some degree. What sets him apart from most social critics is that he does not merely focus on current American society but instead analyzes Western Civilization as a whole and sometimes the "human condition" in its broadest sense. In Slan, his first and most famous novel, some of the principal social themes of van Vogt's career are brought forward, although they are sketchy and confused.

The situation of Slan seems borrowed from the events of World War II, during which the novel was written. The "slans" — millions of mutated humans who are telepathic — are systematically hunted down and murdered by the agents of a worldwide police state.

The persecution of the slans is similar to the persecution of European Jews by Nazi Germany, and the secret police resemble those of Nazi Germany and the Soviet Union...