**This is from guest blogger Cassandra K.**
First of all, I don't sway toward moral subjectivity in the general sense, but many of my own personal questions with strict objectivity are addressed here by Harman and so I do find his argument compelling. It seems true to me that we often make moral judgments because we assume that the agent in question aligns with our own moral compass, so to speak. And the situations we find most unsettling and puzzling seem to be the situations in which the agent is decidedly not guided by our compass (Harman's Hitler example). In this way, it seems plausible that we might make two sorts of moral judgments: 1. comparatively, as in when we assume that the agent has reasons for their action and that those reasons coincide with our own and 2. externally, where we recognize that we are not on the same moral grounds as the agent and thus don't have the "implicit agreement" Harman discusses. Harman is only concerned with the first type of moral judgment, and it seems that he thinks the other form holds less meaning in terms of moral judgments.
I also think there's something to his claim that in some cases we may not have reasons for our actions, morally speaking. He cites that "there might be no reasons at all for a being from outer space to avoid harm to us; that, for Hitler, there might have been no reason at all not to order the extermination of the Jews" (44) and I think this is right. In fact, I think morality is the type of thing that often transcends rationality. We often struggle to rationalize our own moral beliefs and "it is because I say it is" or "it just works for me" is a pretty common base rationale for our personal moral systems.
As a last thought, it seems that our "objective", standardized form of morality is really nothing but a consensus (whether cultural or otherwise) on what we accept to be true. This is how laws are formed that are intended to govern what is right and wrong for a society, country, or other establishment. Where there are communities, accepted communal guidelines for morality are needed. Here is where I found Harman's account the most interesting, because it does seem to give relativism a defense. His account of "agreement" sounds a lot like how the world seems to work in actuality. True, there may be moral outliers who have no moral qualms with murdering people and stealing and all of the other things that we've deemed "immoral" (and thus illegal) by societal standards, but as Harman states, these people are moral "outlaws."
In short, I wasn't expecting to be persuaded by Harman's account of relativism but because he addresses both many of my personal questions about objectivity and many of my concerns with relativism, I found his argument quite compelling. I'd be interested to hear from people who didn't find it compelling (kudos being a more devout objectivist) and their reasons for it.