The paper examines "Campbell's Law": "The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor." The examination of measurability leads to explaining the reason for existence of a class of unmeasurable phenomena. The author describes a kind of habitus in which a strong taboo against measuring must exist by necessity, not by choice. The taboo is, in effect, a result of degradation of a certain kind of habitus. And finally, the paper demonstrates under which conditions the Campbell's law is in effect, and how we can mitigate its effects in social decision-making.