Summa Theologica

We must now consider in particular blasphemy against the Holy Ghost: under which head there are four points of inquiry:

(1) Whether blasphemy or the sin against the Holy Ghost is the same as the sin committed through certain malice?

(2) Of the species of this sin;

(3) Whether it can be forgiven?

(4) Whether it is possible to begin by sinning against the Holy Ghost before committing other sins?