Mr. Williams argues that, among the Koiari-speaking people of Papua, 'the ideal, or "first choice" marriage should be between first cross cousins, and that other unions are a substitute for them'. Thus a man prefers to marry his mother's brother's daughter, and a woman her father's sister's son. Analysts will note that this form of marriage provides the best compromise between the desire for incest and the incest taboo. Presumably this is one reason why it is regarded as ideal.