What Is the Sin of Blasphemy against the Holy Spirit, and Why Is It Unforgivable (Mark 3:28-30 and Parallels)?

This article is a comprehensive examination of the sin of blasphemy against the Holy Spirit. Despite numerous attempts to definitively answer the question of the nature of this sin in Christian history and today, it still appears to be a crux interpretum. The first step is to comprehensively present the status quaestionis and attempt to systematise existing research. The lack of consensus among scholars justifies the need to address this topic from a broader research perspective. The first step in exegetical analysis is a meticulous examination of the synoptic passages in Mark 3:28–30, Matt 12:31–32 and Luke 12:10 in their narrative contexts. This article argues that the essence of the sin of blasphemy against the Holy Spirit is the rejection of the revelation offered by God in Jesus Christ and of God Himself as the revealed God, i.e. apostasy. However, each Evangelist approaches this issue differently, placing emphasis on different aspects. This article also asserts that Luke, probably inspired by Q 12:10, attempts to remove this teaching from its local narrative context and make it universal. This article also examines other texts (Heb 6:4–6, 1 John 5:16, and Gos. Thom. 44) that broaden the theological and cultural context for interpreting the gospel teaching on blasphemy against the Holy Spirit, but they do not add much new content.