What constitutes a felony-murder rule?

"The felony-murder rule operates (1) to posit the existence of malice aforethought in homicides which are the direct causal result of the perpetration or attempted perpetration of all felonies inherently dangerous to human life, and (2) to posit the existence of malice aforethought and to classify the offense as murder of the first degree in homicides which are the direct causal result of those six felonies specifically enumerated in section 189 of the Penal Code. [Citations.] Thus, 'A homicide that is a direct causal result of the commission of a felony inherently dangerous to human life (other than the six felonies enumerated in Pen.Code, 189) constitutes at least second degree murder.' [Citation.]" (Emphasis original.) (People v. Ireland, supra, 70 Cal.2d at p. 538, 75 Cal.Rptr. 188, 450 P.2d 580.)