The breakdown of the positive/normative distinction is extremely important to understand for Muslims. This is because the idea that values/norms can be separated from facts is false. This means that ethical judgements are involved in all human activity, and Islam provides the best guidance on these judgements. This material is replicated on my Islamic Economics page [Positive/Normative Distinction and Islamic Economics].
Some of what I have already written is given here:
Post-Postivist Approaches to Probability (introduction gives general discussion of failure of positivism) View Download [Filename Post4.pdf, attached below]
The Norms of Positive Economics. (discusses how norms are embedded in apparently positive concepts of economics) Download [File CII02_NormsOfPosEcon.doc, attached below]. This could be broken up into several parts.
Fundamental Welfare Theorems Download (Discussion Paper FunWelf3.doc, draft, with some un-assimilated reference material at end). This paper could be broken up into several parts.