The difficulty faced by those in the social sciences is that it is generally subjective in nature.  In the natural sciences, one deals with elements, in some cases literally, which can be quantified and measured in clear and definite ways.  After all, one ounce of water as measured by one individual should be equivalent to one ounce of water as measured by another individual.  Beyond the surface or apparent similarities, such as color, mass, volume or density, they will be equivalent in terms of molecular composition.  However, how does one measure an abstract construct, such as human behaviors?  Further, how would one define its basic elements?

Take for instance, something as simple of a sense of humor.  If, for some reason, one wished to study this abstract phenomenon, how would one measure it?  We could look at its associated visible manifestations.  We could measure laughter, but we would then need to quantify this structure, perhaps by its frequency, length, amplitude, tone, or pitch?  One could also look at the degree of smiling by its height or number of teeth showing.  However, both of these possibilities are not true or complete measures of the construct of sense of humor, merely it is a measurement of its associated behaviors.

What about measuring something more abstract, such as personality, which is more difficult to quantify?  In the endeavor to determine that which defines personality, we are attempting to define that which makes us individuals.  Can the complex set of behaviors which distinguishes each one of us be distilled and categorized into a set of variables? 

So the question becomes, if something as complex as personality may be nearly imposilbe to define in clear-cut terms, why do we bother?  The answer, put simply, is that we humans *want* there to be a clearly defined answer.  We like knowing that 1 plus 1 equals 2, and to know it is comforting.  We want, nay demand, that everything must happen as a result of cause and effect, and the define those causes.  How often have you heard, or even yo yourself said, "There *must* be a reason why this has happened."?

And so we search.  And we catagorize.  And we define.  And we continue to seek out those clear-cut fomulas to describe the world around us, that we *know* have to exist.