I have had great difficulty with this question. I have spent countless hours examining my beliefs and weeding out those I have found no basis for, or at the very least recognizing and accepting them as such: beliefs. 

One that I have been currently interested in is the effect of an observer on the results of an experiment. The idea the outcome of an experiment will tend towards the result expected or desired by the experimenter, has been accepted in the field of psychology since the 1950s. Nowadays, psychologists will use "double-blind" experiments to prevent their data from being skewed. Some quantum researchers even call into doubt the reliability of mechanical (non-human, non-concious?) modes of recording data, as these too are essentially quantum objects.

However, this effect has rarely been take into account in the physical sciences. And certainly not at the classical level.

The special theory of relativity and quantum theory both acknowledge the effect of the observer and the manner of observation on the results of an experiment. 

My experience and the experiments I've read about lead me to believe that an observer and the way in which one observes will affect a system.  I'm not exactly sure how, but....

I feel that this belief is very destabilizing. Many scientists do not want this belief to become an accepted "fact" for it would call into question just about every scientifically "proven" Truth that we have arrived at through experimentation.

Another aspect of this sticky situation to remember is that these Truths or "facts" are nearly always generated through inductive rather than deductive logic.

They are based on the repetition and repeatability of results. They cannot be proven True, only verified again and again. They cannot be proven true, only false.

And then again, deductively arrived at results often result in paradox anyway. So once again I've returned to the point that the statement A=-A must not be complete. At this point I must refer you to Hegel as the only convincing proof I've found that A includes -A in it's definition just as -A includes A in its definition. (Visualize a yin-yang symbol to appreciate this) - and that they must be the same, inclusively, in essence.

man, that got esoteric pretty quickly. Damn regressions.