Baruch Spinoza, also known as Benedictus de (E)Spinoza, was a Dutch philosopher, largely misunderstood until after his death. His work would influence renowned philosophers and scientists, even Albert Einstein. Spinoza's attempts to quantify thought and from it to deduce truths has been a source of much debate and criticism as he explores God and Nature in an unconventional manner.
The Jewish community wherein Spinoza grew up consisted mainly of Jews whose ancestors had fled during the Portuguese Inquisition, converted to Christianity to avoid persecution, and then converted back to Judaism. Spinoza's grandfather was one such person and Spinoza's father converted back to Judaism. Spinoza's upbringing was considered fairly typical, his father being a warden of the synagogue and Jewish school although he was exposed to some less-than-traditional teachings. However, despite his great promise, he never completed any advanced learning of the Torah and the family business became his priority. Frances van den Enden, who would later be labelled "atheist," became a sort of mentor to Spinoza and, although Spinoza did respectfully mourn his father, as his Jewish faith demanded, his questioning of such basic foundations as The Pentateuch or Torah and the connection to Moses, caused him to become increasingly distant from his community. He did not take his decisions lightly and his alienation was not preferred but, for him, was a result of being unable to verify or support the so-called "truths" presented to him. Spinoza longed for someone to provide a more valid proof, whereupon he would "admit defeat" but, without any such refute, he could no longer accept what he saw as irrational teachings:
Although I have been educated from boyhood in the accepted beliefs concerning Scripture, I have felt bound in the end to embrace the views I here express."
Contrary to belief at the time, Spinoza did not intentionally set out to denounce his religion but his insistence that God is Nature, rather than a revered and totally separate being, prevented him from being able to continue his support and he ceased his contributions to the synagogue. By July 1656, such was the extent of the split that he was excommunicated by a "writ of cherem" by the Talmud Torah congregation of Amsterdam. It was a damning and particularly harsh expulsion and Spinoza even tried to express his beliefs that he was simply orthodox in his views. His attempts at apology were never accepted.
Interestingly, although he was influenced by and befriended many Christians, he never felt the desire to convert to Christianity. His beliefs are seen as secular but, in fact, he has a strong spiritual association and the secular nature of his beliefs revolve around his refusal to accept norms and rules rather than any worldly associations. As his excommunication remained in force, and he never accepted any other religion, he is a "secular" Jew.