It has been proper to consider fear in connection with hope, because it is the other side of hope.
We have a sure and certain hope of eternal happiness, as far as God is concerned; we have a sober fear, as far as we ourselves are concerned, lest we offend God, and be separated from Him and so lose our eternal happi*ness. That this hope and fear is a virtue, and that it is our duty to cooperate with God when He inspires it in us, will become clear from another angle, if we consider briefly the two vices which are opposed to hope. The first of these is presumption.
We presume by relying too much either on our own powers or on the mercy of God. Thus, for instance, the Pelagians have the sin of presumption, because they think that man can attain salvation by the exercise of his own powers, and that the help of God is not necessary but only useful. And all persons who give up the practice of religion, not because they think the creeds false, nor because they think the Christian moral ideals wrong, but because they think they are competent to pursue those ideals by themselves, have this sin of presumption. Others sin by presumption when they rely too much on the loving kindness of God, as for instance that God will forgive us whether we repent or no: and that He will give us grace even if we do not bother to use the sacraments. Very often this kind of pre*sumption is made a handle for sin, as when we say that "we may as well be hanged for a sheep as a lamb", meaning it is just as easy for God to forgive, or that He will anyway forgive, a grave sin as a small one, or twenty sins as one sin. And the whole attitude towards God expressed in the phrase "Ie bon Dieii'", and the tendency to postpone amendment of life to one's old age, borders on this sin of presumption.
And it is a sin, first, because it maintains a false and dishonourable view about God, —that He does not really mind about sin.
Secondly, because this attitude causes us to neglect the means of grace and forgive*ness, and is one form of blasphemy against the Holy Spirit. It makes the Holy Spirit powerless.