It seems not improbable that the unlucky character of the number
thirteen may have arisen from its being the number of the intercalary
month. Though the special superstition against sitting down thirteen
to a meal is, no doubt, associated particularly with the Last Supper,
the number is generally unlucky as a date and in other connections. And
this is not only the case in Europe, but the Hindus, Persians and
Parsis also consider thirteen an unlucky number; and the Muhammadans
account for a similar superstition by saying that Muhammad was ill for
the first thirteen days of the month Safar. Twelve, as being the number
of the months in the lunar and solar years, is an auspicious number;
thirteen would be one extra, and as being the intercalary month would
be here this year and missing next year. Hence it might be supposed
that one of thirteen persons met together would be gone at their
next meeting like the month. Similarly, the auspicious character of
the number seven may be due to its being the total of the sun, moon
and five planets, and of the days of the week named after them. And
the number three may have been invested with mystic significance as
representing the sun, moon and earth. In the Hindu Trinity Vishnu
and Siva are the sun and moon, and Brahma, who created the earth,
and has since remained quiescent, may have been the personified
representative of the earth itself.