Question:
What is blasphemy against the Holy Ghost (Mark 3:22-29)?

Answer:
We see from the above portion that to blaspheme against the Holy Ghost was to say that Jesus was casting out demons by the power of Satan.

However, the Holy Ghost was the power whereby Christ cast out demons (Acts 10:38), so this accusation was blasphemy against the Holy Ghost. This sin could only be committed when Christ was here on earth doing miracles, but it was very serious, for Christ said that it could not be forgiven.