My previous remarks have shown where things start; this will give an idea of where they end up. AKA Why not be moral?

Why would we find moral rationality intrinsically valuable? We must presume 
that being reasonable about conflicts of interest is separate and distinct from 
other forms of reasonableness, whether about inferences, quantities or 
nomological relations. In short, we will not try to get an ought from an is. 
Still, we can distinguish at least three characteristics of morality-specific 
rationality that appear attractive in and of themselves: its defensibility, its 
facilitation of cooperation, and its communal inclusiveness. 

 

First, morality is essential for the rational defensibility of one's actions. 
In any conflict of interest, there will be a clear-cut difference between 
following morality and following self-interest: between the right thing to do 
and a course of action that disregards the interests of others. Only a moral 
action is rationally justifiable to others: that is, only the right thing can 
be rationally defended to the others involved in a conflict of interest [FN 
Various authors have remarked on the importance of justifiability in ethics; 
Singer, Scanlon, who else?]. 

 

Second, morality represents the only means of obtaining rational cooperation. 
Thus, it is an optimal strategy for fostering mutual effort:  obviously, moral 
options provide the least grounds for rational disagreement [FN Qualify vav 
inoptimal fairness]. On the contrary, self-interested options, in virtue of 
their disregard of the interests of others, inherently encourage disunity. The 
benefits of cooperation, of avoiding disunity, are indisputable. 



Third, morality is necessary for inclusion and participation in the rational 
community. Every time you selfishly disregard the interests of another, you 
establish a relation of enmity, not just with that person but with every 
reasonable individual. As Locke puts it, "such men are not under the ties of 
the commonlaw of reason ... and so may be treated as beasts of prey" [FN 2nd 
Treatise, Ch. 3, Sec. 16]. If you are not to disassociate yourself from the 
common good and put yourself at odds with the rational community, you must be 
moral.