Are Ethical Propositions Meaningful?, Subjectivity vs. Objectivity. Options

[NoSex]

When I ask if ethical propositions are meaningful, I mean to ask if there is an objective quality (in that a proposition could be considered true, or false) in the case of ethical concerns.

For example, if I am to say that, "It is wrong to engage in premarital sex," can such a proposition be considered to be either true or false? If so, how do we know that such a proposition is of an objective quality, and further, how do we gain knowledge of its true objective status (the truth)?

I hold that ethical propositions are merely reflections of our own personal sentiments (imposed by our biology and environments) and I point to the immense heap of sociology study revolving around the social construction of norms and mores. From what we know, morality appears to be geographical. Depending on where one lives, a human being will experience very different sociological pressures, which seem to largely determine his or her moral feelings.

I also appeal to the naturalistic theory, the absence of evidence for objectivity, and to (evolutionary) psychology to outline the subjectivity of morality. Essentially, I take Hume's position in embracing the "Is-ought-problem," and by affirming that men base their moral positions on their own sentiment, and nothing more. I hold the position that ethical propositions are, in large, meaningless, and can not be considered to be either true or false.

"...morality is determined by sentiment. It defines virtue to be whatever mental action or quality gives to a spectator the pleasing sentiment of approbation; and vice the contrary." - - David Hume

Discuss.