As I write this preface, the world faces unbridled polarisation. Not far from here, the streets of Barcelona are burning due to violent riots, driven by postmodern identity politics and recalcitrant doxastic narcissism. Worldwide, clashes of irreconcilable, often extravagant, conceptions shape current controversies over key social issues and global challenges. Political campaigns spread disinformation as routine, aimed at increasing the isolation and radicalisation of social groups. As a result, authoritarian governments are flourishing among consolidated democracies, such as the United States, Brazil, Poland, Italy, Hungary, the United Kingdom, and Mexico. In other countries, such as France, Denmark, the Netherlands, and Finland, populists parties that propose regressive policies are gaining momentum, promoting the fracture of civic epistemology. This political situation emerges from a lower level phenomenon: echo-chambers of information elicited by filter bubbles and consumer-oriented algorithms. These days, people do not need demagogue politicians or professional charlatans to bring them into contact with, and embolden them to accept, disinformation. Instead, the generalised post-truth situation must be considered a pathology of communication that affects almost all dimensions of our cultural landscape: as hot cognition boosts the rejection of evidence-based discussion over identity-related issues, critical thinking is widely perceived as threatening to internalised partisanship and ingroup bias. Predictably, unfounded beliefs thrive under these conditions. Influential groups successfully promote alternative epistemologies through the denial of scientific facts — e.g. anthropogenic climate change, scientific consensus on the safety of vaccination, or well-documented disinformation on Brexit and the like. Science and universities are exploited in order to defend corporate interests. Fake news, corrupt journalism, and other forms of manipulation of public opinion goes unpunished. Social networks, as the dominant model of interpersonal communication, are a hotbed of epistemic agitation. In general terms, fact acceptance has come to be understood as a tribal process, thus leaving behind modern standards of public reason and critical assessment. This situation is not new: humanity has always been involved in all sorts of biases and dishonest motives. Nevertheless, the current upsurge of irrationality arises from its technical intensification. This special issue is aimed at aiding understanding of this state of affairs, as the philosophical analysis of pseudoscience and post-truth is a subject with great social relevance — a fascinating journey through the dark side of human cognition, not sufficiently taken into account within current philosophical discussions. Despite not having clearly delineated sections, it is structured in three thematic clusters. The first cluster (Vacura, Edis, Cuevas-Badallo and Labrador Montero, Torcello, Vega, and my own contribution) deals with the general elucidation and ramifications of post-truth. The second cluster (Hansson, Stamenkovic, Kreimer, Perez-Gonzalez, and Ruse) analyses specific instances of disinformation and misconceptions, particularly in relation to pseudoscience as a social affair and organised scepticism. Lastly, the third cluster (Cernin, Gascon, Manninen, and Pigliucci) is composed of a heterogeneous set of reflections on the cultural implications of post-truth and pseudoscience, including education and virtue epistemology. I would like to thank the authors who have participated in this special issue. As a guest editor, I’m proud of having worked with you all, and of the magnificent manuscripts included in this monograph. Moreover, I would like to thank the editor-in-chief of this journal, Paulo Velez Leon, for his kind invitation and his courageous support.