I'm taking a research class and the professor reviewed qualitative and quantitative approaches and the thinking behind them. Quantitative analysis of course involves variables that are strictly measurable; everything must be measured using numbers. The qualitative approach is more personal and may rely on data like recorded interviews. She explained that the qualitative approach emerged in the '60's as a counter to the quantitative, masculine, everyone can be explained as a number approach adopted first by the military and then everyone else. A qualitative approach recognized that it is difficult to reduce people to numbers and statistics, and that maybe research should start collecting data directly from the people instead of inferring data from quantitative tests. This would allow researchers insight into the people themselves and allow us to recognize the multiple realities of peoples' experiences.
The quantitative approach assumes a single reality, an external reality that is independent of people's experiences. There is a right answer to every question, and a quantitative approach allows access to that solitary truth. Qualitative researchers on the other hand assert that there is not one reality, but multiple realities that we can only discover through a qualitative approach. Each person has their own reality, and these would be missed or ignored through a strictly quantitative approach. This thinking is part of what might be considered postmodernism (or relativism): the belief that there is no absolute truth but instead there are multiple truths. For example, many see Thomas Kuhn's work, The Structure of Scientific Revolutions, as showing that even scientific knowledge of that one reality is suspect and that therefore not one reality but multiple realities exist. The reality of any given person then depends on culture, language, and so on.
I believe that the language used in this sort of dialogue is all wrong. When relativists (or qualitative researchers) say that there are multiple realities they are simply mistaken. What they should say is that there are multiple perspectives. For example, on an episode of the radio program This American Life the story of a missing boy was told. When a boy was found, two families claimed it was their boy, as both had indeed lost their son. Each were convinced that the boy belonged to them; in other words they each had their own realities. But clearly the boy could only have been from one family and not both, and therefore perspective is the more appropriate term. I think perhaps the fear is that perspective is not a strong enough word, and that different people's experiences will be ignored unless they are described as a reality. I hope no relativist would actually claim that the boy actually was both of the boys that had gone missing. It seems clear that there is only one external reality: the boy could have only been from one family or the other.
How then do we interpret the clear value of qualitative research and ideas like those of Kuhn's? The answer is that relativists were wrong about what is relative. They would claim reality itself is not singular. They are making a claim about ontology, or what actually exists. The proper claim should be about epistemology, or what we can know. There is one reality, but our access to it is fuzzy at best. Even scientific knowledge, which usually enjoys a vaulted epistemic status, is far from certain, as the work of Kuhn and others has shown. It is a mistake however to confuse what I will call epistemological relativism (the uncertainty of all knowledge; even scientific, quantifiable knowledge) with ontological relativism (that there actually exists more than one reality).
To sum up, we should replace talk of "multiple realities" with talk of multiple perspectives, being sure to appreciate and take seriously how people perceive reality. For example, my perspective right now is that it's time to order a pizza. How can I be sure that this is actually a reality, not just my perspective? My wife has told me so.