David Hume - The Origin of Moral Distinctions (A Treatise of Human Nature)

    Something I have been reading in David Hume's A Treatise of Human Nature that has stuck out to me is his theory of the origin of moral distinctions, which as far as I can tell seems to be correct. In summary, his theory of the origin of moral distinctions is that we draw moral distinctions based on sensations of pain or pleasure that we receive from external objects, and the kind of pain or pleasure we receive from external objects such as humans causes us to draw moral distinctions.
    For example, if a white person believes it is immoral to force a black person into slavery the root of that moral distinction is the sensation of unpleasantness or pain that the white person receives from the idea of they themselves being forced into slavery because of their own skin color. They receive a sensation of unpleasantness that leads to a passion of aversion from the idea of they themselves being subjected to slavery because of their skin color, and the resemblance between this idea and the idea of a black person being forced into slavery allows them to easily transition that passion of aversion from themselves to the black person being forced into slavery. If there was no sensation of unpleasantness or pain that lead to a passion of aversion all there would be is passions and facts in the external objects as we examine them, and there would be no basis for drawing any moral distinctions. We would have no pain or pleasure to transfer to the idea of their situation in order draw a moral distinction.  
    I would also like to add another example for what Hume is saying. When a moral distinction is made even in religion  the root of that distinction is still a passion of aversion that stems from a sensation of unpleasantness. For example, religions such as Christianity or Islam will say homosexuality is immoral ultimately because of a passion of aversion to that concept. That passion of aversion stemmed from a sensation of unpleasantness that at some point someone had due to it being different from them and not what they considered normal. Stances against homosexuality is now considered immoral because society has shifted to where a passion of aversion to mistreatment of homosexuals is taking priority to a passion of aversion someone has from them simply being different.