While the penalties attached could not completely deter such killings, they were at least severe enough to minimize them. The faufreluches, the class system, was very carefully preserved. Only under extraordinary circumstances could a House Minor achieve the status of a House Major, or an individual rise above the class into which he or she was born. The age-old route of marrying upward was always available, of course, but was rarely used; young women of noble birth were most often married to a nobleman of their family's choice, while noblemen were far more inclined to take an attractive commoner as concubine titan as spouse. Upward mobility usually was possible only for those who could achieve exceptional success in business, war or politics. And in such cases, it was far from assured. The consent of the emperor was needed to elevate an individual, and that of both the emperor and the Landsraad to elevate a House. The (Tamers of the Convention did not wish to spark discontent by making advancement impossible, but it was vital to their social system that the process be kept difficult. Other sections formalized the prohibitions laid down by the Butlerian Jihad, less than 750 years past and stiU fresh in Galactic memory.