Alexander Solzhenitsyn, in volume I of The Gulag, argued that totalitarianisms share ten things in common:

1. Fear.  “Fear was not always the fear of arrest.  There were immediate threats: purges, inspections, the completion of security questionnaires—routine or extraordinary ones—dismissal from work, deprivation of resident permit, expulsion or exile.”
2. Servitude.  Internal passports, legal prohibitions on buying, selling, or renting housing stock greatly limited one’s ability to escape, the right to exit was denied.
3. Secrecy and Distrust.  “This universal mutual mistrust had the effect of deepening the mass-grave pit of slavery.  The moment someone began to speak up frankly, everyone stepped back and shunned him: ‘A provocation!’  And therefore anyone who burst out with a sincere protest was predestined to loneliness and alienation.”
4. Universal Ignorance.  Because of number three, no one could trust the information of another, or trust another with information.  This resulted in true isolation of the right-thinking person.
5. Squealing on one another, further eroding any trust that might exist.  Without trust, civilization proved impossible.
6. Betrayal, therefore, became a norm.  Sons betrayed fathers, daughters betrayed mothers, husband betrayed wives, and supposed best friends betrayed one another.
7. Corruption, as a result, became endemic, as the betrayers became professionals, earning positions, status, and wealth for their inside information, true or false.  Frequently, one informed on a person simply to acquire something the other person had or had created.  The informer then became the owner and the “creator.”
8.  Lies.  “The permanent lie becomes the only safe form of existence, in the same way as betrayal.  Every wag of the tongue can be overheard by someone, every facial expression observed by someone.  Therefore every word, if it does not have to be a direct lie, is nonetheless obliged not to contradict the general, common lie.  There exists a collection of ready-made phrases, of labels, a selection of ready-made lies.
9. Cruelty.  “And where among all the preceding qualities was there any place left for kindheartedness?  How could one possibility preserve one’s kindness while pushing away the hands of those who were drowning?  Once you have been steeped in blood, you can only become more cruel. . . . And when you add that kindness was ridiculed, that pity was ridiculed, that mercy was ridiculed—you’d never be able to chain all those who were drunk on blood.”
10. Slave psychology.  The system, ultimately, made men impotent.