There are plenty of logical positivists out there, I was trained by
one on my internship. Needless to say, I found his approach to
clinical psychology rather interesting. After learning repeatedly to
assess the individual, not the test results, this gentleman's
approach of interpretting test reults without ever seeing the patient
(he had technicians administer MMPI's forr example) was quite
different.
At the other end of the continuum, there are the radical
constructivists, including Waazlawick, Maturana, and others (see
Mahoney _Human Change Processes_) who do not necessarily buy in to
assuming any objective reality.
I've found that Kellian constructivism, termed trivial constructivism
(although I don't like to think of it as trivial at all) meets
somewhere in the middle, that's why there is enough room on the
metatheoretical teeter totter to balance both extremes.
AJ