I think couple of things can be observed to support living virtuously without needing to resort to invoking any supernatural cause:
1. Observe a fundamental law of nature: Whatever we give to the nature is what nature grows and gives us back in many times over. We give seed to earth it gives back us a full fledged plant. We genuinely appreciate people and spread happiness in return we receive the same.
2. Observe our conscience: Even though you can denounce religion and God but at least we experience and listen to our conscience, inner voice regularly. Not sure how much modern psychology has done research over this stuff but at least in yogic circles it's been extensively covered as a fact that the more you abide by virtues in your thoughts, speech and conduct, the more calmer, peaceful and contented you will be (lesser inner conflict/clear conscience etc.) And that's fundamental to lasting happiness
To me #1 sounds like an appeal to nature without basis. It sounds a little like “The Secret”—positive actions have positive reactions—which I haven’t seen evidence of sufficiently to make a law of.
I don’t know what “listen to our conscience, inner voice regularly” or “abide by virtues in your thoughts“ mean.
Regarding the conscience, it's blabbering of the mind. while you're busy in some activity you may not notice it, but it's there in your subconscious. To observe it, just sit for few minutes and try to see thoughts originating in mind.
This constant chatter, which may include grudges, guilt, complaints, fear, phobia, jealousy, envy , worries etc. are emotions that spring up when we're too focused on ourselves in our life. The virtuous, kind actions that we do for others help in expanding our consciousness; our prospective toward life changes and consequently the self-obsession decreases resulting in greater inner peace, calm and contentment.
1. Observe a fundamental law of nature: Whatever we give to the nature is what nature grows and gives us back in many times over. We give seed to earth it gives back us a full fledged plant. We genuinely appreciate people and spread happiness in return we receive the same.
2. Observe our conscience: Even though you can denounce religion and God but at least we experience and listen to our conscience, inner voice regularly. Not sure how much modern psychology has done research over this stuff but at least in yogic circles it's been extensively covered as a fact that the more you abide by virtues in your thoughts, speech and conduct, the more calmer, peaceful and contented you will be (lesser inner conflict/clear conscience etc.) And that's fundamental to lasting happiness