The three requirements for mortal sin were stated in chapter fifteen. Here the notion of grave matter will be clarified, with particular reference to current theories of fundamental option and to St. Thomas Aquinas’ discussion of the question. The conclusion will be that the act of faith is a Christian’s fundamental option, and that the distinction between grave and light matter can be explained by the different ways in which immoral acts can be related to faith. Problems about sufficient reflection and full consent will be considered in chapter seventeen.
Why do not all sins involve grave matter? Some suggest that a sin in light matter is one unlikely to subvert a good fundamental option. Current theories of fundamental option must be rejected. However, they offer an insight which can be synthesized with St. Thomas’ account of the distinction between grave and light matter to provide a more adequate solution to the problem. Faith is the fundamental option of Christian life; those kinds of acts are light matter which conflict neither with faith nor with its implicit requirements.