Actually the principle of truth is considered as a primary value in social science as Principles are the basic scientific, logical, or ethical moral "facts" that arise from experience, knowledge and values and on it we build our movements and our thinking.
Scientific and logical principles are derived from experience and testing, from knowledge and from logical analysis, or from theory. That is, free from bias and untested hypotheses.
Whereas Ethical and moral principles are where values come from. These principles result from deep-rooted values and beliefs