Sample members taking the survey would sometimes leave answers blank or respond that they did not know.This issue would be okay if we knew the missing values were random, however most often there is systematic reasons for why some people leave answers blank thus presents bias into the model. (commons.trincoll.edu)
But there is a systematic reason why political theories with a preferential view of self - interest have taken politics to be wholly an instrumental activity. (religion-online.org)
This point has been pressed not only for the systematic reason that it appears to be a real weakness in the Thomist position but also because much of modern Protestant thought can be understood only against the background assumption that philosophical theology of the Thomist type must necessarily lead to conclusions that diverge from the Biblical understanding of God. (religion-online.org)