During the period we have considered, the city passed through five distinct stages of political organization. The government at first, as we have seen, was an elective monarchy, the electors being a patriarchal aristocracy. After the invasion of the Sabines, there was a union with that people, the sovereignty being held by rulers chosen from each; but it was not long before Rome became the head of a federal state. The Tarquins established a monarchy, which rapidly degenerated into an offensive tyranny, which aroused rebellion and at last led to the republic. We have noted that in Greece in the year 510 B.C., the tyranny of the family of Pisistratus was likewise overturned. During all these changes, the original aristocrats and their descendants firmly held their position as the Populus Romanus, the Roman People, insisting that every one else must belong to an inferior order, and, as no body of men is willing to be condemned to a hopelessly subordinate position in a state, there was a perpetual antagonism between the patricians and the plebeians, between the aristocracy and the commonalty. This led to a temporary change under Servius Tullius, when property took the place of pedigree in establishing a man's rank and influence; but, owing to the peculiar method of voting adopted, the power of the commons was not greatly increased. However, they had made their influence felt, and were encouraged. The overturning of the scheme by Tarquin favored a union of the two orders for the punishment of that tyrant, and they combined; but it was only for a time. When the danger had been removed, the tie was found broken and the antagonism rather increased, so that the subsequent history for five generations, though exceedingly interesting, is largely a record of the struggles of the commons for relief from the burdens laid upon them by the aristocrats.