Epicureanism

Epicurus founded his  philosophical school around 307BC. He was was an atomic materialist, following in the steps of Democritus. His determinism led him to a general attack on superstition and divine intervention.  He  believed that the greatest good was to seek modest pleasures in order to attain a state of tranquility, ataraxia, and freedom from fear, as well as absence of bodily pain, aponia, through knowledge of the workings of the world and the limits of one's desires. The combination of these two states is supposed to constitute happiness in its highest form.

His follower, the Roman poet, Titus Lucretius Carus, was the author of the a didatic poem'De Rerum Natura', 'On the Nature of the Universe'. Lucretius identifies superstition (which he refers to as 'religio') with the notion that the gods/supernatural powers created our world or interfere with its operations. He argues against fear of such gods by demonstrating through observations and logical argument that the operations of the world can be accounted for entirely in terms of natural phenomena—the regular but purposeless motions and interactions of tiny atoms in empty space—instead of in terms of the will of the gods.

Atheists have often delighted in quoting the following line from his poem, thus giving religion a bad name:

Tantum religio potuit suadere malorum- so potent was superstition in persuading to evil deeds.

Needless to say, when the early Christians began using the word 'religio' to denote their faith a few centuries later, it had already acquired a different a different meaning.

Lucretius' poem was printed in numerous editions during the Renaissance, and influenced many early Pantheists.