Numbering the Ptolemies is a modern invention; the Greeks distinguished them by epithet (e.g. "Philopator") or nickname (e.g. "Auletes"). The number given here is the present consensus, but there has been some disagreement in the 19th century about which of the later Ptolemies should be counted as reigning. Since older sources may give a number one higher or lower, epithets are the most reliable way of determining which Ptolemy is being referred to in any given case.