A man's ethical behaviour should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death.
God! sing, ye meadow-streams, with gladsome voice!
Ye pine-groves, with your soft and soul-like sounds!
And they too have a voice, you piles of snow,
And in their perilous fall shall thunder, God!
What art Thou then, my God? what, but the Lord God? For who is Lord but the Lord? or who is God save our God? Most highest, most good, most potent, most omnipotent; most merciful, yet most just; most hidden, yet most present; most beautiful, yet most strong; stable, yet incomprehensible; unchangeable, yet all-changing; never new, never old; all-renewing, and bringing age upon the proud, and they know it not; ever working, ever at rest; still gathering, yet nothing lacking; supporting, filling, and overspreading; creating, nourishing, and maturing; seeking, yet having all things.
In the beginning (if there was such a thing), God created Newton's laws of motion together with the necessary masses and forces. This is all; everything beyond this follows from the development of appropriate mathematical methods by means of deduction.