The modern concept of ideology was established by the liberal politician and philosopher Destutt de Tracy, with the objective of creating an all-embracing and general science of ideas, which followed the sensualist and empiricist trend initiated by Locke that culminated in the positivism of Comte. Natural selection and immunity are two key concepts in the history of biology that were strongly based on the Malthusian concept of struggle for existence. This concept wrongly assumed that population grew faster than the means of existence. This “natural” law contained implicitly the idea that the poor and least gifted would not survive. This idea led to the progressive development of the concept of natural selection, whose definitive version was given by Darwin. Mechnikov took the concepts of struggle for existence and natural selection and conceived infectious diseases as a struggle between a host and its invader, the so-called phagocytosis theory. This theory created the necessity to possess mechanisms to discriminate between the own and the foreign, and led to the conception of the immune self. These concepts were not developed from ideas coming from perceptions or sensations, but from ideas coming from their values: individual interest, inevitable inequality, property, utility and profit. Values are ideals that constitute an ideological matrix which exerts a numinous activity and influence the development of our future actions. In consequence, science and its practice cannot avoid and ignore the values that drive them and impulse them towards certain directions.