Although the investigation of the various normative factors and their interaction makes up a large part of normative ethics, it does not exhaust the field. For even if we had an adequate account of these matters, questions would still remain concerning the foundations of normative ethics (recall the distinction between factors and foundations drawn in 1.4). It is, after all, one thing to say which factors possess genuine moral significance; it is quite another thing to say what grounds or explains the moral significance of those factors.
Of course, whether a given factor is relevant in a particular case depends on the specific facts of that case. But what explains why a given basic normative factor ever makes any difference at all to the moral status of our actions? Why do the basic normative factors have the moral relevance that they do? Foundational theories in normative ethics try to answer these questions. They offer rival accounts concerning the grounding or basis of the normative factors. Similarly, they try to explain why the basic normative factors have the precise contours and contents that they do, and why the various factors interact in the precise ways that they do.
It is perhaps worth noting explicitly that in calling such theories "foundational" I do not mean to be claiming that they are basic or primary in an epistemological sense. That is, I am not claiming that our knowledge of the foundations of normative ethics is somehow uniquely "prior" to, or more secure than, our knowledge of the normative factors themselves (though this is, to be sure, one possible view). Of course, as I have noted previously (in 1.4), it does seem likely that commitment to one or another theory at the foundational level will sometimes lead us to embrace particular views at