Sin has its source in freedom: it arose because man turned towards himself instead of towards God.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“The creature is not a being distinct from God. The creature subsists in God, and God manifests Himself in the creature in an ineffable manner. “The Holy Trinity loves Itself in us and in Itself;† It sees and moves Itself.” Sin has its source in freedom: it arose because man turned towards himself instead of towards God. Evil does not have its ground in God, for in God there is no idea of evil. Evil is not-being and has no ground, for if it had a ground it would be necessary. Evil is a privation of good. The Logos is the principle that brings the many back to the One, and man back to God;” source