*Also, Elliot hashed out a lot of this argument with me several weeks ago, so I credit him with some of my articulations. Consider him a contributor to my blog!
As most economists can *hopefully* agree upon, the foundations of economics lay in a few choice axioms regarding human behavior. If we were to equate this to the sciences, we'd likely call these the baseline principles, or "laws" that macro-theories are based upon. The idea is that these baseline principles are timeless, consistent, predictable, universally accepted ("proven" in some cases, or unable to be disproven), and inhabit all interactions in both micro and macro application. Everything that stems from these laws must conform, at their foundation, to the aforementioned parameters. This sets up a pretty solid model for approximating phenomena (within the scope of the laws).
Science on the whole, with this understanding, can be considered a positive field. Within the sciences, approximations of phenomena (for the vastvastvast majority, negligible-exception most part) can be empirically-derived, and such empirically-derived data lends itself to the ever-expanding model of our universe. The reason model is italicized is that it is simply that: a model, not reality. Although empirical data is the most logical derivation of/closest thing we have to reality, our limitations as data-collectors reject the possibility of a perfect model from which to predict the rest of reality. We can get close, but we'll never be perfect. Therefore, our approximations of other things based off of model should be taken with a grain of salt.
However, just because our model isn't perfect doesn't mean that it isn't pretty damn good at predicting things. In fact, it's the best thing we have! Because we're so rigid about what we allow in, and so anal about taking misinformation out, we've developed a pretty reliable, relevant, and predictable (though not perfect) model. And we do want to predict reality; we want to find out how entities behave, and in what conditions, and to what degree, and to what magnitude, and to what accuracy. This is where science gets normative. In the interest of time (and your interest) I'll skip my proof, and get to the punchline: After something has been proven to death (and never disproven), it becomes regarded as a normative statement. Walter Block's "Triangles have 180 degrees" idea is a perfect example, and as my high school science teacher loves to add "Gravity exists" is another one. Each has its roots in empirical data, but it is referenced as a universal truth that doesn't need to be proven each time it's referenced.
The reason for bringing this all up is twofold:
Firstly, I wanted to draw the relationship between normative and positive statements, and will sum it up here:
Normative: relating to an ideal standard or model
Positive: Information derived from sensory experience, logical and mathematical treatment is the exclusive source of all authoritative knowledgeAs I stated previously, I viscerally fall into the positive camp, but I'm not afraid of the normative. For as I've described, the normative is based on the positive, and the two should not be regarded as mutually exclusive.
Secondly, I want you to go back through what I've written and replace the word "science" with "economics". That's really the main point of all this. I feel as though economics and science are not really all that different. In fact, just as chemistry and biology are branches off of the physics tree trunk (that is to say, they all subscribe to the same fundamental laws), I believe too that economics is a very distant, budding branch. As a branch, it's very young, and deals with a level of complexity that humans, given our technological/psychological limitations at this point in time, may not be equipped to efficiently or effectively model.
To back up a bit, when you look at economics, you see that there are, similarly, a set of laws or "axioms" in this case, that dictate the behavior of all economic phenomena. I would guess that these axioms arose and are perpetuated much like the fundamental laws of physics (empirically), but are now regarded normatively (see the end of paragraph 4 if you don't follow). From these axioms, and the ever-increasing collection of economic data, a model of economics is being developed, and can be used to predict realities, much like science!
The catch in the economic model is, very unlike the sciences, human behavior is a heavily complex amalgamation of principles/laws/axioms that we have yet to fully understand. Not only do we not really have a grip on what we at our core, but we understand very little about how we change, and change our minds. We have a few basic basic basic axioms (such as, humans "act" and "want"... no duh), but that's all we can really rely on. To our credit, that's a pretty good start in economics, and gives us some foundation to begin feeling around (however blindly). When we start exploring and observing economics, we start seeing trends and patterns that economists quickly tend to want to make "normative statements". This isn't necessarily a bad thing. Aggressively clinging to perceived absolutes is what we've done for centuries in many fields (even science). Consider the "World is Flat" or the "Sun Revolves Around the Earth". Yes: for the time being, utilizing that information to run the world, or to predict other things may yield some pretty funky results, but the important thing is that we're interested and we're trying. Hopefully, as soon as someone sees that things aren't adding up, they'll experiment, and either back up the observation with some evidence, or disprove it with some evidence. It isn't until we get some damn evidence that anything can be considered in the "normative": it must be proven empirically, then regarded as normative. That's when we'll start making some progress.
My last thought before I let you go: it is because of all of our past misconceptions in all fields all across the board that I firmly believe no one should be so rigid in their beliefs. ESPECIALLY IN ECONOMICS for, like, a thousand reasons. Because economics deals with variable human behavior, it unfortunately has to deal with the fact that humans, human values, behaviors, cultures, social rules, etc. etc. etc. are constantly changing; that is, the conditions are constantly changing under which economists can run experiments (which as scientists are well aware, makes taking data extremely difficult, and often not worth it if the conditions are changing too much too quickly). We're hard to pin down and look at instantaneously, because we can't, by our very nature, be instantaneously solved. Unfortunately that's all human behavior is, and that's all economics STUDIES! Again, it's not impossible to do, just extraordinarily inefficient given our capabilities. What economists can do (and have done) is look for the empiric trends in human behavior during specific time periods, and see if such behaviors transcend their initial conditions. When they do, there's a pretty good case to be made for it being closer to universally true, and closer to being a normative statement. Economics hasn't been around long enough to have many of those, which is why I don't think any economist should parade around with too many normatives (beyond the axioms). More economists have been proven wrong than right, and the "right" normative statements that have stuck around have only done so because they've withstood the test of time and a wide variety of test conditions.
Anyway, my closing point is that economists should be very humble and careful with their beliefs, and learn that there are no normatives before positives. If they don't heed that warning, they may just look like the Catholic Church in 1616 trying to arm wrestle with Galileo's Heliocentric model of the universe...they got their asses kicked.