Objection 1. It would seem that the character of Order necessarily presupposes the character of Confirmation. For in things subordinate to one another, as the middle presupposes the first, so does the last presuppose the middle. Now the character of Confirmation presupposes that of Baptism as being the first. Therefore the character of Order presupposes that of Confirmation as being in the middle.
Objection 2. Further, those who are appointed to confirm should themselves be most firm. Now those who receive the sacrament of Order are appointed to confirm others. Therefore they especially should have received the sacrament of Confirmation.
On the contrary, The apostles received the power of order before the Ascension (John 20:22), where it is said: "Receive the Holy Ghost." But they were confirmed after the Ascension by the coming of the Holy Ghost. Therefore order does not presuppose Confirmation.
I answer that, For the reception of Orders something is prerequisite for the validity of the sacrament, and something as congruous to the sacrament. For the validity of the sacrament it is required that one who presents himself for Orders should be capable of receiving them, and this is competent to him through Baptism; wherefore the baptismal character is prerequisite for the validity of the sacrament, so that the sacrament of Order cannot be conferred without it. On the other hand, as congruous to the sacrament a man is required to have every perfection whereby he becomes adapted to the exercise of Orders, and one of these is that he be confirmed. Wherefore the character of Order presupposes the character of Confirmation as congruous but not as necessary.
Reply to Objection 1. In this case the middle does not stand in the same relation to the last as the first to the middle, because the character of Baptism enables a man to receive the sacrament of Confirmation, whereas the character of Confirmation does not enable a man to receive the sacrament of Order. Hence the comparison fails.
Reply to Objection 2. This argument considers aptness by way of congruity.
Source: Summa Theologica (New Advent)