Is a Ph.D. in Philosophy from a Russian University essential when applying to U.S. Ph.D. full funding programs in Philosophy? Is the world rank of that Russian University important for the purpose ?

No. A PhD would't be necessary. We have had Russian students in our PhD program, and they did not come to us with PhDs. The most important thing will be evidence of philosophical ability. Course records matter; so do informative letters of reference. The writing sample is particularly important. And if there are publications (not required) they would be useful too.

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