Objection 1. It seems that martyrdom is not an act of the greatest perfection. For seemingly that which is a matter of counsel and not of precept pertains to perfection, because, to wit, it is not necessary for salvation. But it would seem that martyrdom is necessary for salvation, since the Apostle says (Romans 10:10), "With the heart we believe unto justice, but with the mouth confession is made unto salvation," and it is written (1 John 3:16), that "we ought to lay down our lives for the brethren." Therefore martyrdom does not pertain to perfection.
Objection 2. Further, it seems to point to greater perfection that a man give his soul to God, which is done by obedience, than that he give God his body, which is done by martyrdom: wherefore Gregory says (Moral. xxxv) that "obedience is preferable to all sacrifices." Therefore martyrdom is not an act of the greatest perfection.
Objection 3. Further, it would seem better to do good to others than to maintain oneself in good, since the "good of the nation is better than the good of the individual," according to the Philosopher (Ethic. i, 2). Now he that suffers martyrdom profits himself alone, whereas he that teaches does good to many. Therefore the act of teaching and guiding subjects is more perfect than the act of martyrdom.
On the contrary, Augustine (De Sanct. Virgin. xlvi) prefers martyrdom to virginity which pertains to perfection. Therefore martyrdom seems to belong to perfection in the highest degree.
I answer that, We may speak of an act of virtue in two ways. First, with regard to the species of that act, as compared to the virtue proximately eliciting it. On this way martyrdom, which consists in the due endurance of death, cannot be the most perfect of virtuous acts, because endurance of death is not praiseworthy in itself, but only in so far as it is directed to some good consisting in an act of virtue, such as faith or the love of God, so that this act of virtue being the end is better.
A virtuous act may be considered in another way, in comparison with its first motive cause, which is the love of charity, and it is in this respect that an act comes to belong to the perfection of life, since, as the Apostle says (Colossians 3:14), that "charity... is the bond of perfection." Now, of all virtuous acts martyrdom is the greatest proof of the perfection of charity: since a man's love for a thing is proved to be so much the greater, according as that which he despises for its sake is more dear to him, or that which he chooses to suffer for its sake is more odious. But it is evident that of all the goods of the present life man loves life itself most, and on the other hand he hates death more than anything, especially when it is accompanied by the pains of bodily torment, "from fear of which even dumb animals refrain from the greatest pleasures," as Augustine observes (Q83, qu. 36). And from this point of view it is clear that martyrdom is the most perfect of human acts in respect of its genus, as being the sign of the greatest charity, according to John 15:13: "Greater love than this no man hath, that a man lay down his life for his friends."
Reply to Objection 1. There is no act of perfection, which is a matter of counsel, but what in certain cases is a matter of precept, as being necessary for salvation. Thus Augustine declares (De Adult. Conjug. xiii) that a man is under the obligation of observing continency, through the absence or sickness of his wife. Hence it is not contrary to the perfection of martyrdom if in certain cases it be necessary for salvation, since there are cases when it is not necessary for salvation to suffer martyrdom; thus we read of many holy martyrs who through zeal for the faith or brotherly love gave themselves up to martyrdom of their own accord. As to these precepts, they are to be understood as referring to the preparation of the mind.
Reply to Objection 2. Martyrdom embraces the highest possible degree of obedience, namely obedience unto death; thus we read of Christ (Philippians 2:8) that He became "obedient unto death." Hence it is evident that martyrdom is of itself more perfect than obedience considered absolutely.
Reply to Objection 3. This argument considers martyrdom according to the proper species of its act, whence it derives no excellence over all other virtuous acts; thus neither is fortitude more excellent than all virtues.
Source: Summa Theologica (New Advent)