Flourished represents the date a person 'flourished'. This is used mostly for persons whose date of birth is completely unknown, and we only have information about the date of some of their publications. This date (or the median date) is the date 'flourished'. For comparison purposes we may use this for persons whose date of birth is known. In this case we assume that all people 'flourish' in their mid-thirties. This is approximately true for philosophers, it may not be true of poets, musicians and mathematicians, who tend to flourish earlier. Also of rock stars, although we know the birthdays of all of those.