Whether Venial Sin Is a Disposition to Mortal Sin?
Objection 1: It would seem that venial sin is not a disposition to
mortal sin. For one contrary does not dispose to another. But venial
and mortal sin are condivided as contrary to one another, as stated
above (A. 1). Therefore venial sin is not a disposition to mortal sin.
Obj. 2: Further, an act disposes to something of like species,
wherefore it is stated in _Ethic._ ii, 1, 2, that "from like acts
like dispositions and habits are engendered." But mortal and venial
sin differ in genus or species, as stated above (A. 2). Therefore
venial sin does not dispose to mortal sin.
Obj. 3: Further, if a sin is called venial because it disposes to
mortal sin, it follows that whatever disposes to mortal sin is a
venial sin. Now every good work disposes to mortal sin; wherefore
Augustine says in his Rule (Ep. ccxi) that "pride lies in wait for
good works that it may destroy them." Therefore even good works would
be venial sins, which is absurd.
_On the contrary,_ It is written (Ecclus. 19:1): "He that contemneth
small things shall fall by little and little." Now he that sins
venially seems to contemn small things. Therefore by little and
little he is disposed to fall away together into mortal sin.
_I answer that,_ A disposition is a kind of cause; wherefore as there
is a twofold manner of cause, so is there a twofold manner of
disposition. For there is a cause which moves directly to the
production of the effect, as a hot thing heats: and there is a cause
which moves indirectly, by removing an obstacle, as he who displaces
a pillar is said to displace the stone that rests on it. Accordingly
an act of sin disposes to something in two ways. First, directly, and
thus it disposes to an act of like species. In this way, a sin
generically venial does not, primarily and of its nature, dispose to
a sin generically mortal, for they differ in species. Nevertheless,
in this same way, a venial sin can dispose, by way of consequence, to
a sin which is mortal on the part of the agent: because the
disposition or habit may be so far strengthened by acts of venial
sin, that the lust of sinning increases, and the sinner fixes his end
in that venial sin: since the end for one who has a habit, as such,
is to work according to that habit; and the consequence will be that,
by sinning often venially, he becomes disposed to a mortal sin.
Secondly, a human act disposes to something by removing an obstacle
thereto. In this way a sin generically venial can dispose to a sin
generically mortal. Because he that commits a sin generically venial,
turns aside from some particular order; and through accustoming his
will not to be subject to the due order in lesser matters, is
disposed not to subject his will even to the order of the last end,
by choosing something that is a mortal sin in its genus.
Reply Obj. 1: Venial and mortal sin are not condivided in contrariety
to one another, as though they were species of one genus, as stated
above (A. 1, ad 1), but as an accident is condivided with substance.
Wherefore an accident can be a disposition to a substantial form, so
can a venial sin dispose to mortal.
Reply Obj. 2: Venial sin is not like mortal sin in species; but it is
in genus, inasmuch as they both imply a defect of due order, albeit
in different ways, as stated (AA. 1, 2).
Reply Obj. 3: A good work is not, of itself, a disposition to mortal
sin; but it can be the matter or occasion of mortal sin accidentally;
whereas a venial sin, of its very nature, disposes to mortal sin, as
stated.
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