Premise: Some, like French, Spanish, Italian, and Portuguese, had more in common with one another than they did with, say, German, English, Swedish, Danish, and Dutch, which, in turn, bore only a remote resemblance to Russian and Polish, on the one hand, and the two extant varieties of, say, Gaelic, on the other.

Hypothesis: The evolution of each language family was determined by the spread of various European cultures.
Relation: neutral