-Is Psychology anything more than the mirror of societal ideology? -
The everyday business of the scientific endeavour constitutes the search for verifiable, testable and repeatable claims about reality. Some of the time something rather amazing and intrinsic of the universe can be accurately characterised. If this happens then science is able to make solid predictions that turn out to be empirically supported by data. If this scenario happens reliably and consistently, then this characterisation of the universe, or theory, can begin to be considered an accurate model of reality with predictive capability, a law of science.
'Hard', or 'basic', sciences such as Physics or Chemistry (this should hopefully not infer that the study of fundamental particles is by any means 'easy') deals with the simple stuff, in principle. Compared with biological systems, matter is relatively simple. It is this 'simplicity' that allows magnificent, evidence based, laws to be appropriately defined and extrapolated across the whole expanse of space and time.
From many points of view, homo sapiens are very very complicated.