This dissertation explores the "Is"—"Ought" problem (IOP) as it relates to natural law theory (NLT). It begins with a brief analysis of the type of "ought" precepts upheld by traditional natural law theorists as well as a consideration of the precise nature of the IOP. Chapter two considers the attempts of Searle and Gewirth at establishing that it is possible validly to derive an "ought" conclusion from "is" premises and asks whether their attempts can be imitated successfully by those who wish to uphold the basic claims of NLT. Chapter three considers whether it is possible to bypass the IOP by beginning with premises concerning the de facto desires of human agents. Chapter four consists of an analysis of Geach, Veatch, McInerny, MacIntyre, and Lisska who put forth the solution of returning to the Aristotelian-Thomistic understanding of the telos, function, or essence of the human person. In Chapter five the new natural law solution is analyzed; and in Chapter six an overall critique is offered.

The overarching thesis of this dissertation is that—although each solution is in some way problematic—the solution of new natural law theorists is the least problematic if one wishes to implement an "ought" that is moral, prescriptive, non-relativistic, determinate, and related to the common good.