Objection 1. It would seem that hope is not a theological virtue. For a theological virtue is one that has God for its object. Now hope has for its object not only God but also other goods which we hope to obtain from God. Therefore hope is not a theological virtue.
Objection 2. Further, a theological virtue is not a mean between two vices, as stated above (I-II, 64, 4). But hope is a mean between presumption and despair. Therefore hope is not a theological virtue.
Objection 3. Further, expectation belongs to longanimity which is a species of fortitude. Since, then, hope is a kind of expectation, it seems that hope is not a theological, but a moral virtue.
Objection 4. Further, the object of hope is something arduous. But it belongs to magnanimity, which is a moral virtue, to tend to the arduous. Therefore hope is a moral, and not a theological virtue.
On the contrary, Hope is enumerated (1 Corinthians 13) together with faith and charity, which are theological virtues.
I answer that, Since specific differences, by their very nature, divide a genus, in order to decide under what division we must place hope, we must observe whence it derives its character of virtue.
Now it has been stated above (Article 1) that hope has the character of virtue from the fact that it attains the supreme rule of human actions: and this it attains both as its first efficient cause, in as much as it leans on its assistance, and as its last final cause, in as much as it expects happiness in the enjoyment thereof. Hence it is evident that God is the principal object of hope, considered as a virtue. Since, then, the very idea of a theological virtue is one that has God for its object, as stated above (I-II, 62, 1), it is evident that hope is a theological virtue.
Reply to Objection 1. Whatever else hope expects to obtain, it hopes for it in reference to God as the last end, or as the first efficient cause, as stated above (Article 4).
Reply to Objection 2. In things measured and ruled the mean consists in the measure or rule being attained; if we go beyond the rule, there is excess, if we fall short of the rule, there is deficiency. But in the rule or measure itself there is no such thing as a mean or extremes. Now a moral virtue is concerned with things ruled by reason, and these things are its proper object; wherefore it is proper to it to follow the mean as regards its proper object. On the other hand, a theological virtue is concerned with the First Rule not ruled by another rule, and that Rule is its proper object. Wherefore it is not proper for a theological virtue, with regard to its proper object, to follow the mean, although this may happen to it accidentally with regard to something that is referred to its principal object. Thus faith can have no mean or extremes in the point of trusting to the First Truth, in which it is impossible to trust too much; whereas on the part of the things believed, it may have a mean and extremes; for instance one truth is a mean between two falsehoods. So too, hope has no mean or extremes, as regards its principal object, since it is impossible to trust too much in the Divine assistance; yet it may have a mean and extremes, as regards those things a man trusts to obtain, in so far as he either presumes above his capability, or despairs of things of which he is capable.
Reply to Objection 3. The expectation which is mentioned in the definition of hope does not imply delay, as does the expectation which belongs to longanimity. It implies a reference to the Divine assistance, whether that which we hope for be delayed or not.
Reply to Objection 4. Magnanimity tends to something arduous in the hope of obtaining something that is within one's power, wherefore its proper object is the doing of great things. On the other hand hope, as a theological virtue, regards something arduous, to be obtained by another's help, as stated above (Article 1).
Source: Summa Theologica (New Advent)