The author analyses one of the few examples of Polish case law in criminal cases where the notion of mercy is used. In the author’s opinion, the commented decision of the Supreme Court deserves a mixed, partly approving and partly critical assessment. The use of the notion of mercy in criminal law in general must be assessed positively. What is negative, however, is the manner in which the Supreme Court did so, which amounts to a laconic thesis, nearly without justification, about the importance of mercy for the process of making criminal law valuations. The commented decision of the Supreme Court of 2018 is also, at the same time, an impetus to make some remarks about the role of philosophical argumentation in criminal law.