Thus, the Hopi and Navajo Indians have both occupied for a long period the same part of northeastern Arizona and on the environmental theory we should therefore expect among them the same mode of life. In this, however, we are thoroughly disappointed. The Hopi are intensive farmers who succeed in raising crops where white agriculturists fail; the Navajo also plant corn but to a distinctly lesser extent and under Spanish influence have readily developed into a pastoral people, raising sheep for food and wool. Though the same building material is available, the Hopi construct the well-known terraced sandstone houses with a rectangular cell as the architectural unit, while the Navajo dwell in conical earth-covered huts. North American ceramic art attains one of its highwater marks among the Hopi, while the pottery of the Navajo is hopelessly crude in comparison. Cotton was raised by the Hopi, but there is no trace of its use by the neighboring people. What is true of the material aspect of native life applies equally to its less tangible elements. There is at least one marked difference in the sexual division of labor: with the Hopi it is the man’s business to spin and weave while this work falls to woman’s share among the Navajo. The Hopi were always strict monogamists, while among the Navajo polygamy was permissible. In conjunction with their agricultural pursuits Hopi ceremonialism centered in the magico-religious production of rain; the Navajo applied often the identical ritualistic stock-in-trade to the cure of sickness. A stringent regulation of the Navajo social code forbids all conversation between son-in-law and mother-in-law; but the Hopi merely view the taboo as a Navajo idiosyncrasy. The general cast of Hopi psychology, as fashioned by Hopi society, is that of an eminently peaceable population; the Navajo rather recall in their bearing the warlike and aggressive tribes of the Plains. Where resemblances occur, as _e.g._, in the objective phase of the native cults, we are able to prove that the parallelism is due not to an independent response to environmental stimuli, but to contact and borrowing. But quite apart from such cases, the basic differences in Hopi and Navajo civilization show that the environment alone cannot account for cultural phenomena.