Some thoughts on enlightened self-interest as the basis for morality
(What follows is a slightly rambling expansion on some of my comments about morality in the post below. What I'm hoping to show is that enlightened self-interest can provide us with a strong reason to act in a "moral" way. It's intended as a conversation starter rather than a definite pronouncement on the subject.)
Enlightened self-interest is different from sentiment or whim – I may save someone's life because I like the look of them, but such an action does not count as truly moral.
The vast majority of human beings are bound together by certain innate desires (security, companionship, contentment, procreation, etc.) which are harder (or downright impossible) to realise outside of the social setting. These desires, as well as forming the bedrock of all civilisation, provide the foundation of secular morality.
Immoral acts constitute those which undermine the realisation of these desires.
For example: I desire safety for myself and those I care about. If I make a habit of killing those who get in my way then I not only provide no reason for others to help keep me alive, I actually provide them with a reason to kill me – as I represent a significant threat to them and their loved ones. The best way to realise my desire is to promote the safety of all in the expectation that they will, in turn, ensure my safety. If I kill, or tolerate killers, such an arrangement is impossible to maintain.
This differs from whim in that reason is employed to consider the total effect of my actions. If someone makes me angry whim may tell me to kill them while reason tells me that such an action will be counter-productive.
(Obviously, most people aren't that keen on killing in the first place, no matter how angry they get – but I'm assuming worst case scenario to show the strength of enlightened self-interest).
As another example: I'm able to provide for myself and my loved ones much easier in a social setting than on my own. Bartering services and goods allows me a much comfier lifestyle than I'd enjoy in isolation – catching and cooking your own food (not to mention building a house, dealing with illness, etc.) is much harder than turning up at work each day and sitting in front of a computer. In order for bartering to work there has to be a basic level of trust between individuals. If I go around lying about everything then people will cease to trust me and so cease to work with me. (The social aspect of my life will also be significantly reduced). So not only do I have a strong reason to be truthful but also a strong reason to promote truthfulness in society as a whole.
An immoral individual is one at war with the rest of society – undermining their chance to realise significant desires.