Rational moral standards

I think maybe I'm getting this figured out; I think I will ignore the G+ business and stay here.

Abortion is a major moral question by not of course the only one, and the big question is how do we make moral decisions.  In my experience most people, even when they say otherwise, are guided by their conscience, with a dollop of utilitarianism thrown in.

They may say they are guided by authority (the Church, the Bible, the Q'uran) and sometimes quote passages, but these are not rule books and contain no rational law and only some vague guidance ("Do unto others, etc.).  No the main source of guidance is what feels right to us -- our conscience.

Where does conscience come from?  It seems to me more than likely that we have an instinctive ability to form a conscience, but the details are "filled in" during early life from our peers and our culture in general.  This is why different people from different cultures feel this or that is right or wrong (look for example at the evolution of attitudes about slavery in our own culture).

Conscience then is a fairly good guide, but not an infallible one.  Slavery is wrong in and of itself, so is carrying out raids on the neighboring tribe's hen-house, or torture, or being dishonest to foreigners, even though many in history have not seen such things as against their particular conscience.

Nowadays, this is generally understood, so people try to find a rational basis for their moral standards, and most opt for a fairly simple utilitarianism, even though (and I don't intend to get into them now) there are many objections to this approach.  It does work better most of the time than either dogmatic authoritarian religion based rules or from our culturally received conscience.

In short, assuming one is not a sociopath and therefore does want to do what is right, one has to realize that in many borderline situations there is no easy answer and one is better sitting back and thinking about it, perhaps in the context of the various ethical systems that have been proposed, rather than just going with what feels right.