A religious movement by Lelio and Fausto Sozzini, born in Italy and spread in Europe in the XVII century; it denied that Christ was a God, claiming instead he was a man who got eternal life because he incarnated the right values and become a model. He become immortal only later on. Thus, man can become immortal if he behaves exactly following the Christian principles.
It follows the doctrine of mortalism: souls aren’t immortal, they die with the body. Behaving in a good manner becomes a reward to get eternal life.
Socinianism challenged a lot of religious institutions and was considered “dangerous” even by other christian heresies.
According to some scholars, John Locke was inspired by Socinianism in constructing his idea of personal identity, in particular focusing on the matter of the mortality of the soul.
Isaac Newton was a Socinianist.