||One of Mendelsshon's major religio-philosophical works. Phaedon, or On the Immortality of the Soul, the work which made him famous throughout Europe as the "German Socrates," was a novel effort at translation and commentary on the Phaedo of Plato. The work begins as a strict translation of the Platonic dialogue, but rapidly diverges into its own independent work, as Mendelssohn supplies arguments of his own and others more convincing, he believed, than those supplied by Plato's Socrates. He seeks to demonstrate the rationality of the belief in the existence of G-d. He treats the subject as a principle of general metaphysics and man's universal religion of reason.
Mendelssohn's favorite proof for G-d's existence is a modification of the ontological argument: Man finds the idea of a Supreme Being in his consciousness. Since this idea cannot have arisen out of man's limited and fragmented experiences - we have no direct knowledge of anything remotely resembling the idea of divine perfection - it is a priori and belongs to the category of concepts that precede all experience and enable us to comprehend the universe, including space, time, and causality. Although these concepts do not arise from experience, they are not subjective because they determine the character of universal experience. Further, there is a necessary connection between the concept of an absolutely perfect being and his existence, a being which is absolutely real, or perfect, must have existence among its attributes; otherwise, it would be lacking the full complement of its unconditioned possibility.
Mendelssohn campaigned for the termination of the Jewish ghettoes and the entrance of the Jews as equals into German society, efforts which were aided by his first-ever translation of the Pentateuch into German, and the publication of his political treatise Jerusalem, which argued for religious toleration within the state, and against the control of civil society by religious institutions, based on the idea that religious conscience could not be legislated, and that man's actions must be guided by reason. These arguments formed the basis of the Haskalah (Jewish Enlightenment) movement in Eastern Europe and the Russian Pale of Settlement, which liberated these Jewish communities from the Hasidic rabbinate degraded by cabalism and superstition. Mendelssohn's influence in Germany and America led to the formation of the Jewish Reform movement.