 On 21 March 1816 , at the age of seven years , Mendelssohn was baptised with his brother and sisters in a home ceremony by Johann Jakob Stegemann , minister of the Evangelical congregation of Berlin 's Jerusalem Church and New Church . Although Mendelssohn was a conforming ( if not over @-@ zealous ) Christian as a member of the Reformed Church , he was both conscious and proud of his Jewish ancestry and notably of his connection with his grandfather Moses Mendelssohn . He was the prime mover in proposing to the publisher Heinrich Brockhaus a complete edition of Moses 's works , which continued with the support of his uncle Joseph Mendelssohn . Mendelssohn was notably reluctant , either in his letters or conversation , to comment on his innermost beliefs ; his friend Devrient wrote that " [ his ] deep convictions were never uttered in intercourse with the world ; only in rare and intimate moments did they ever appear , and then only in the slightest and most humorous allusions " . Thus for example in a letter to his sister Rebecka , Mendelssohn rebukes her complaint about an unpleasant relative : " What do you mean by saying you are not hostile to Jews ? I hope this was a joke [ ... ] It is really sweet of you that you do not despise your family , isn 't it ? " Some modern scholars have devoted considerable energy to demonstrate either that Mendelssohn was deeply sympathetic to his ancestors ' Jewish beliefs , or that he was hostile to this and sincere in his Christian beliefs . 
