Their use was twofold; they were either labourers in the workshop and the field, or domestic members of the villa or the palace, and their presence in either capacity was fraught with important political consequences for Rome. Their cultivation of the mechanical arts and crafts made the Roman noble’s household self-sufficient[567] and the competition of the free artisan almost a hopeless task. In the country they were gradually replacing both the free labourer and the yeoman farmer. The advantage of cheap labour, which could not be snatched from the master’s hands by the needs of distant wars, was at an early period recognised by the nobles in the cultivation of their vast estates.[568] After the acquisition of the province of Sicily, which supplied cheap food to Rome, slave labour on the large estates became an economic necessity; for it was the only condition on which corn could now be productively grown. The lot of the plantation slave, unknown to his master and exposed to the mercies of the overseer, was a shameful parody of the earlier domestic servitude. Yet the state did nothing. The slave possessed no rights, as in the time when he, perhaps, required none. In the case of domestic slavery, the moral influence of an intellectually superior race was often an adequate substitute for the absence of rights, and a further _solatium_ was found in the door of emancipation which was ever open to the favourite. The Roman was not ungrateful, and he recognised that it was the slave who made him an individual power in the world. The unequalled administrative capacity of men like C. Gracchus, Crassus, Caesar, and Pompeius, which has found no parallel in the modern world, was largely due to their absolute command of men of perhaps less originative power, but often of greater capacity for combination and detail than they.