Schneider was born to Catholic and liberal parents in Ettenheim. He studied medicine and specialised in ophthalmology. In 1898 he settled in Neunkirchen, Saarland and started his practice. From the end of the century he showed an interest in the burgeoning social democracy and studied the works of Marx, Engels, Bebel and Kautsky. After World War I during the November Revolution he was a member of the workers' council, which was later dissolved by French troops on 1 December 1918. In Neunkirchen he was responsible for the welfare of the sick. In 1919 he was a founding member of the Independent Social Democratic Party of Germany (USPD) in Neunkirchen. He was selected as a frontrunner at the USPD council election on 11 July 1920, and was elected to the Ottweiler district council and to the Neunkirchen town council. After the unification of parts of the USPD with the Communist Party of Germany, Schneider broke with his old party.