From the dictionary:
The belief, based solely on reason, in a God who created the universe and then abandoned it, assuming no control over life, exerting no influence on natural phenomena, and giving no supernatural revelation.
The founding fathers were not so much social darwinists, which really developed fully in the 19th Century with it's most powerful proponent being Herbert Spencer. The founding fathers were basically libertarian (classical liberals) at least as far as white males were concerned. They also were strong proponents of a limited federal government. Any government welfare programs were limited to the states. Social Security is blatantly unconstitutional under a originalist interpretation.