Besides for other reasons (adduced below) this appears necessary, because one of the most important scientific uses that has been made of the different human systems of kinship is one that presupposes a certain definite meaning, as given to the terms of kinship in very low societies. In Morgan's deductions a very important part is played by the assumption that kinship is always understood in terms of consanguinity; in particular that it was understood thus by primitive man; that in all (even the lowest) societies all ideas of kinship were essentially based upon the community of blood, established in the case of the mother by her share in bearing, in that of the father by his part in procreation. Only by assuming that these facts were known to the lowest, prehistoric savages, could Morgan draw inferences from systems of kinship terms about the forms of sexual intercourse. If, on the other hand, the relation between sexual intercourse and birth escaped the knowledge of primitive men, they could not have based their idea of kinship upon community of blood between father and offspring; hence there could be no connection between forms of sexual intercourse and forms of kinship as conceived by primitive man. Whether there could be connection between marriage, defined sociologically, and kinship is another and more complicated problem. In any case Morgan uses throughout his book the word consanguinity, and he defines it as the tie of common blood arising from the sexual act. In other words he sets forth the problem in a simplified and incorrect form. The question how kinship may be conceived in a given society, especially in a low one, naturally presents itself as a very important point of investigation. As in the following pages there will be question more or less exclusively of the individual relation between parents and children, the present discussion may be fittingly restricted to the individual parental kinship in Australia. In the second part of this chapter facts giving some insight into the aboriginal collective ideas of kinship are set forth; and in the following chapter other different facts will be brought forward in order to complete the definition of _individual parental kinship_. But in accordance with what has been just said, it is needful to have some guiding principle in collecting this material, and this will now be looked for. This discussion, being only concerned with the Australian facts, does not pretend to be complete, but perhaps if the results are worked out so as to suit our modern European concept of kinship as well as the Australian one, it might, should it be correct, be applicable also to other societies.[515] Let us now proceed to give the general definition of kinship and in the first place to indicate which are its constant, uniform factors found in all societies. [515] Of course by result is meant a general formula for kinship.