d. Finally, the general trustworthiness of the writer or writers must be taken into account.
2º. If we are told that there are no slaves, it is very probable that slavery really does not exist, for slavery is a phenomenon rather easy to observe, and the ethnographers are generally inclined to use the word in a too wide rather than in a too restricted sense. There is no need here for the extreme scepticism with which we have to receive an assertion of any tribe having no religion[3]. This does not prevent, of course, that if we find the existence of slavery denied by a writer who is generally badly informed, we may reject such an assertion.
3º. The greatest difficulties are presented by those cases in which no mention is made of slavery. Here the utmost caution has to be observed.
a. If it clearly appears from the description, that there are people considered to be the property of others, without the word “slavery” being used, the conclusion is evident.
b. Perhaps some facts are mentioned which make the existence of slavery highly improbable. We shall see that the main source of slavery is captivity in war; so, if it is stated that no captives are made, or that the lot of the captives is something else than slavery, the non-existence of slavery is probable. But even then it is not quite certain: there may still be slaves, acquired by other means. Further: if it is stated that there are no social classes, or if the classes are enumerated and slaves are not among them, there is a strong presumption that slavery does not exist. Yet here too there is no certainty; for slaves, among savage tribes, have not always the aspect of a social class. The description of the [[44]]division of labour between the sexes may also suggest to us the non-existence of slavery. When we are informed that the men do some kinds of work and the women some other kinds, we are inclined to think: if there were slaves, their special work would be mentioned too. But this argument is most dangerous; for the slaves very often have no special kind of work allotted to them.
We see that none of these criteria prove quite reliable. Yet, taken together, they give a high degree of probability. And it is not even necessary that all of them can be ascertained. If an ethnographer, known to be trustworthy, gives us an elaborate description, pretending to be a picture of the whole social life of the tribe he describes, it were a wonder if he had entirely omitted slavery, while it existed; the more so as this phenomenon is not so difficult to recognize. The same argument obtains a fortiori, when several such descriptions of the same tribe exist.
4º. In doubtful cases we may take into account the state of the group to which a particular tribe belongs. It may be that in the general descriptions of a group no mention is made of slavery; that, further, all tribes belonging to this group of which we are well informed prove to have no slaves. If, then, the information we get concerning a particular tribe belonging to the same group, is not complete enough to rely upon, there is a strong presumption that this tribe will be in the same state as the rest of the group, i.e. that it does not keep slaves. Under the same conditions we may suppose that a tribe belonging to a slave-keeping group keeps slaves. The term “group” has to be taken here in a sociological, not in an anthropological or linguistic sense, and its application must be somewhat restricted. It must consist of tribes, that live in somewhat similar conditions and the institutions of which closely resemble each other; e.g. Australia (the continent) is a group in this sense, North America is not. It is almost superfluous to add, that this group-argument may be used only to strengthen existing, but insufficient, evidence.
We confine ourselves here to the phenomena of savage life; therefore we shall exclude the semi-civilized peoples. An exact distinction, however, between these two classes of peoples has [[45]]not yet been made[4]; so we are fully aware of the possibility of mistakes, made here in this respect. As we were not able to apply any exact criterion, we have more or less followed our general impressions, paying most attention to the development of political institutions. So for instance we have excluded the Kabyls of Northern Africa, because their detailed legal system, as described by Hanoteau and Letourneux[5], proves that politically they have passed beyond the stage of savagery. And a developed political organization cannot exist without profoundly marking such an institution as slavery.
We shall find that several savage tribes have to a considerable extent been influenced by civilized or semi-civilized nations. In such cases the question arises: have we to deal here with phenomena of unadulterated savage life? This question is important and deserves full attention. We shall see that many savage tribes in their true aboriginal state have been acquainted with slavery, whereas many others when first discovered did not practise it; so neither the existence nor the non-existence of slavery must necessarily be due to foreign interference; either may be aboriginal, and must be supposed to be so wherever there is not a strong presumption to the contrary[6]. But there are also many cases in which foreign influence has undoubtedly been at work. We must, then, make a distinction. If the influence of the civilized or semi-civilized nation has led to a, so to speak, normal development, i.e. a development, which lies within the limits of primitive culture, we have to deal with a phenomenon of savage life. For instance, commercial intercourse with a nation of higher civilization has brought about an accumulation of wealth and a social differentiation, which render the existence of slavery possible. In such case we may safely speak of slavery as practised by savages, for it is the effect of trade in general, not of intercourse with a [[46]]civilized nation as such, that we have to deal with here. If, on the contrary, there has been an abnormal development, i.e. a development which does not take place in countries inhabited by savages only, the present condition of the savage tribe has no interest to us. For instance, measures have been taken by a civilized nation on purpose to abolish slavery. Then we, for our purpose, must consider the savage tribe concerned as keeping slaves, and pay attention only to the descriptions of its institutions as they were before the abolition.
The ensuing paragraphs will show which savage tribes keep slaves and which do not keep any. The groups into which we have divided the several tribes are mainly geographical, not intended to answer any anthropological purpose. As long as the meaning of the term “race” is so unstable as at present, we think it better not to operate with it. Our groups are nearly the same as those given by Schurtz in his Völkerkunde.