Appendix 2 Fn(177).
According to St. Thomas, sin is present in the human being if sluggishness of mind, debility and lack of consideration arise from affection for what is carnal and evil. We need to note this carefully: shallow-minded people easily persuade themselves that sin is never present when actual advertence is lacking. But all the most reliable writers on morality teach that inadvertence and lack of consideration, as the effect of an evil disposition prior to the will, can itself be sinful. The evil disposition and carnal affection depends on our free will; it is not consented to of necessity. Suarez and other serious authors rightly distinguish between lack of consideration produced by an external (and therefore unwilled and inculpable) cause, and lack of consideration produced by an internal cause, that is, from an evil (and therefore culpable) disposition of will.
It will be helpful to cite the passage where Suarez uses reason and authoritative sources to show that 'it is certain that there is such a thing as willed lack of consideration: St. Thomas taught this expressly in I-II, q. 6, a. 3, ad 3 and a. 7. He says that we can will not to consider something just as we can will not to will, and will not to act. And hence just as something can be indirectly willed without an act of will, so it can be willed without actual consideration on the part of the intellect. In question 73, a. 7, ad 2 he says the same as in the question just quoted, q. 6, a. 8: although pleasure may diminish actual consideration, nevertheless lack of consideration is willed because we have the power either to prevent concupiscence, or to apply our intellect, notwithstanding concupiscence, to consider the matter. Scotus correctly demonstrates this in 2, Distin, 42, q. 1; and ALL THEOLOGIANS AND WRITERS OF 'SUMMAE' presuppose it. . . . The same teaching is found also in Aristotle, 2 De Anim., c. 5, where he speaks about human beings actually understanding when they exercise their will, and in c. 4 repeats the same thing relative to the intellect constituted in its first act. St. Augustine is of the same opinion in 2 De Trinit., c. 3, and in bk. 14, c. 27; often in these books he expertly discusses and enquires what the intellect must do so that the will can apply the intellect to the consideration of some matter.'
After quoting authorities, Suarez gives the reasons. The first is: 'The will can move the intellect to perform an act, and for this reason not all actual lack of consideration is natural and EXTRINSIC; some is INTRINSIC, dependent upon the human will. This was correctly explained by Gabriel in 2, Dist. 22, q. 2, a. 1. For the same reason lack of consideration on the part of the intellect could sometimes be attributed to the will as its true positive, or at least, deprivative cause. Just as affirmation is the cause of affirmation, so privation is the cause of privation.' The second reason - and this is beyond controversy - is that lack of consideration, in the opinion of the authors, is sometimes imprudent and culpable, and therefore willed.
We can add that we are able to do what Christ has commanded, namely, not let our reason sleep but keep it constantly alert to its duties. Hence, we can sin without consideration, and indeed through lack of consideration. Suarez continues: 'Finally, to pray without attention is wrong and culpable because mental distraction can be willed; non-attention is simply non-consideration. Therefore, lack of actual consideration can sometimes and perhaps often be willed.' (Tract. de Volunt. et Involunt., Disp. 4, sect. 3, 8).