Respectfully Quoted: A Dictionary of Quotations. 1989.
Will Durant (18851981)
A great civilization is not conquered from without until it has destroyed itself within. The essential causes of Romes decline lay in her people, her morals, her class struggle, her failing trade, her bureaucratic despotism, her stifling taxes, her consuming wars.
WILL DURANT, Caesar and Christ, Epilogue, p. 665 (1944).