what is social capital?

"those tangible substances [that] count for most of the daily lives of people: nameley, good will, fellowship, sympathy, and social intercourse among the individuals and families who make up a social unit... The individual is helpless socially, if left to helpself... if he comes into contact with his neighbor, and they with other neighbors, there will be an accumulation of social capital, which may immediately satisfy his social needs and which may bear a social potentiality sufficient to the substancial improvement of living conditions in the whole community. The community as a whole will benefit by the cooperation of all its parts, while the individual will find in his associations the advantages of the help, the sympathy, and the fellowship of his neighbors."

written in 1916 by L.J. Hanifan urging the importance of community involvement for sucessful schools, he invoked the idea of "social capital" to explain why.