The term ideology is usually used in three different senses, each of which alludes to a different concept: ideology in the sense originally proposed by Marx and Engels; ideology as a political thought, which ended up being the most frequently used notion; and ideology as a bias that affects the positions that can be adopted in the field of theory. This last notion will be analyzed here; trying to show its difference, but also its relationships, with the other two notions. An attempt will also be made to establish a difference between the notions of ideological bias and of political position in theory.¿QUÉ ES UN SESGO IDEOLÓGICO?