Meanwhile it must be observed that the passage just quoted is not perfectly precise. The larger the society, the greater might be the division of labour and consequent stimulus to invention; but a tribe might be large and yet have little in it of a society, and still less of a division of labour. Without such favouring circumstances as Malthus mentions the progress cannot take place; but even with them it need not; they are therefore not the real motive power. The account of the state of population among the South Sea Islanders,[175] which comes next in order to the chapter on the American Indians, is an illustration of these remarks. These savages live in a fertile country and yet they make no progress. As this is not the only point illustrated, it is worth while to look at the chapter in detail. Malthus begins by observing that population must not be thought more subject to checks on an island than on a continent. The Abbé Raynal, in his book on the Indies, had tried to explain a number of modern customs that retarded population[176] by referring them to an insular origin. He thought that they were caused at first by the over-population of Britain and other islands, and were imported therefrom into the continents, to the perplexity of later ages. But as a matter of fact population on the mainlands is subject to the same laws as on the islands, though the limits are not so obvious to common observation, and the case is not put so neatly in a nutshell. A nation on the continent may be as completely surrounded by its enemies or its rivals, savage or civilized, as any islanders by the sea; and emigration may be as difficult in the one case as in the other. Both continent and island are peopled up to their actual produce. “There is probably no island yet known, the produce of which could not be further increased. This is all that can be said of the whole earth. Both are peopled up to their actual produce. And the whole earth is in this respect like an island.”[177] The earth is indeed more isolated than any island of the sea, for no emigration from it is possible. The question, therefore, to be asked about the whole earth as about any part of it, is, “By what means the inhabitants are reduced to such numbers as it can support?”