The concept of ideology is central to the understanding of the many political, economic, social, and cultural processes that have occurred in the last two centuries. And yet, what is the nature of the different ideologies remains a vague, open, and much disputed question. Many political, sociological, and ideological studies have been devoted to ideology. Very little, on the other hand, has been done from the philosophical field. And this despite the fact that there are undoubtedly many philosophical questions related (...) to ideology and its role in modern industrialized societies. Just a few examples of ideology-related philosophical questions suffice to prove the point: What objects do ideologies deal with? Are the ideologies testable? Are there true ideologies? Do they evolve? How are ideologies related to societies? Is the existence of ideologies inevitable in modern societies? What is the relation of ideology to science? Is science just another kind of ideology? Are we, as human beings, innately predisposed to believe in ideologies? Or, instead, ideologies proliferate through indoctrination and propaganda? Are ideologies necessarily harmful?...and much more. In this article I try to answer some of these questions from a philosophical point of view, taking a materialist approach. I begin by characterizing ideology as a complex, multi-layered concept. Then, I briefly discuss the material systems on which ideological movements operate, that is, societies and concrete human groups. I identify at least 11 different elements that seem to be present in most ideologies, and I compare these characteristics with those of contemporary science and technology. Although some superficial similarities can be identified, there are deep differences that make ideology completely different from science. The similarities, however, are stronger with technology. Ideologies continually evolve with technological advances, social changes, and even with mere fashion. The current fragmentation of ideologies caused by the widespread use of new technologies and social networks has given rise to new phenomena of ideological propagation which, in my opinion, are very dangerous, particularly for open societies. I discuss these processes, within the context of the nature vs nurture debate, along with the question of whether we can get rid of ideologies. (shrink)