Are revealed preferences normative or positive notion? I always thought from my understanding of the terms normative and positive that revealed preferences are a positive concept. For example, saying Anakin prefers grass to sand (i.e. $U(g)\succ U(s)$) is a positive statement. 

My thinking is as follows:


It’s a value free statement 
It’s empirically objectively testable statement. We can just make an experiment where we give Anakin choice of sitting in sandy room vs grassy room and observe preference.
Independent observers would agree on the observed outcome Anakin picking the grassy room.


However, I encountered an opinion that since all preferences derive from underlaying values they are all strictly normative and considering them positive even in the strict sense of revealed preference is a fallacy.

Is the opinion correct? If the opinion is not correct how would you refute it? Just by stating my points 1-3? 

Also I tried to find some sources that would discuss this but google scholar just gives me results that are unrelated to this philosophical issues. I looked in Julian Ress’ philosophy of economics, and Hausmanns anthology but I could not find satisfactory answer there either. Are there any good references for this issue?
However, I encountered an opinion that since all preferences derive from underlaying values they are all strictly normative and considering them positive even in the strict sense of revealed preference is a fallacy.


There's a logical inconsistency here which might help see why it's not a good way of looking at the issue.  What is the key element that is purportedly revealed by dividing the universe into "things normative" and "things positive"?  I would suggest that it is determinism - matters of a positive nature correlate by way of fully deterministic, structurally-modelable processes that are discoverable through repeated experiment.  Think physics - laws guide observables, observables reveal the laws, the laws can be used to predict future observables.  If a tree falls in a forest and no one is around to hear it, physics tells us that it still makes a sound.

Matters of a normative nature correlate only to the extent that a system of "norms" has been set up to enforce them.  Think ethics - morals guide behaviour, behaviour reveals morals, but can morals - absent a normative framework - be used to predict future behaviour?  No - because morals themselves can change, because agents are capable of deception, and because agents may not even have perfect knowledge of their own preferences. Crucially, morals alone are no guaranteed predictor of unexamined human behaviour.

So, I'd argue that your friend's opinion is logically inconsistent because it is a contradiction: in order for it to be true that all preferences derive from underlying values, it must be true that values influence behaviour in a deterministic way according to underlying laws that are, in principle, discoverable through experiment.  That's a pretty weighty claim, in my opinion not at all borne out by the preponderance of evidence - but if it were true, it would mean preferences are in fact positive!

Whether preferences are normative or positive then depends on the assumptions about the agent.  We usually want them to be positive so that we can math about them, and so we make a whole bunch of assumptions about homo economicus that - if true - support that assumption.  But of course, we know that homo economicus is a fiction. So we might suspect that our theory on preferences is at best a useful benchmark to provide context for understanding how people actually behave.