Man is called by nature to live in society; for he needs many things which are necessary to his life, and which by himself he cannot procure for himself. Whence it follows that man naturally becomes part of a group, to procure him the means of living well.He needs this assistance for two reasons.First, in order that he may obtain the elementary necessities of life; this he does in the domestic circle of which he is a part. Every man receives from his parents life and nourishment and education; and the reciprocal aid of the family members facilitates the mutual provision of the necessities of life. But there is a second reason why the individual is helped by the group of which he is a part, and in which alone he finds his adequate well-being. And this is, that he may not only live, but live the good life---which is enabled by the opportunities of social intercourse. Thus civil society aids the individual in obtaining the material necessities, by uniting in the same city a great number of crafts , which could not be so united in the same family. And civil society also assists him in the moral life. From the text, we can infer that a craft ____________.