The author argues against two statements typical of contemporary psychology: first, that the scientist’s activity is always subjective and that science therefore cannot pursue truth; second, that empirical data are objective and do not depend on the person. Although science is a subjective activity, its ambition is to describe reality adequately. Experience tells us that science has both subjective and objective elements. Yet we cannot allow contradictions in science; «anything does not go». If two conceptions are based on two mutually contradictory presuppositions, they cannot be equally true. Sometimes behaviourism, psychoanalysis and cognitivism are described as various descriptions of the same phenomena. The author disagrees with it and argues that only one approach can be correct. The more we can see what is subjective in the text, the better we understand and assess it. Psychologists should report about their preliminary expectations and how much the results of their research match the latter. The author believes that any data claim is an interpretation and as such should be double-checked.