Evidence-based medicine, evidence-based psychiatry and evidence-based development of clinical guidelines are all flourishing today because of developments that have taken place in both science and society. These concepts will be explained and placed in their context. Medical treatment is based on the one hand on scientific knowledge and experience, on the other hand on compassion and consideration for others. Non-specific and relational factors play an important role, particularly in psychiatry and mental health care, but the scientific way of thinking remains as important as ever.