Objection 1. It would seem that in the sacrament of Order a character is not imprinted in connection with all the Orders. For the character of Order is a spiritual power. Now some Orders are directed only to certain bodily acts, for instance those of the doorkeeper or of the acolyte. Therefore a character is not imprinted in these Orders.
Objection 2. Further, every character is indelible. Therefore a character places a man in a state whence he cannot withdraw. Now those who have certain Orders can lawfully return to the laity. Therefore a character is not imprinted in all the Orders.
Objection 3. Further, by means of a character a man is appointed to give or to receive some sacred thing. Now a man is sufficiently adapted to the reception of the sacraments by the character of Baptism, and a man is not appointed to dispense the sacraments except in the Order of priesthood. Therefore a character is not imprinted in the other Orders.
On the contrary, Every sacrament in which a character is not imprinted can be repeated. But no Order can be repeated. Therefore a character is imprinted in each Order.
Further, a character is a distinctive sign. Now there is something distinct in every Order. Therefore every Order imprints a character.
I answer that, There have been three opinions on this point. For some have said that a character is imprinted only in the Order of priesthood; but this is not true, since none but a deacon can exercise the act of the diaconate, and so it is clear that in the dispensation of the sacraments, he has a spiritual power which others have not. For this reason others have said that a character is impressed in the sacred, but not in the minor*, Orders. But this again comes to nothing, since each Order sets a man above the people in some degree of authority directed to the dispensation of the sacraments. Wherefore since a character is a sign whereby one thing is distinguished from another, it follows that a character is imprinted in each Order. And this is confirmed by the fact that they remain for ever and are never repeated. This is the third and more common opinion.
Reply to Objection 1. Each Order either has an act connected with the sacrament itself, or adapts a man to the dispensation of the sacraments; thus doorkeepers exercise the act of admitting men to witness the Divine sacraments, and so forth; and consequently a spiritual power is required in each.
Reply to Objection 2. For all that a man may return to the laity, the character always remains in him. This is evident from the fact that if he return to the clerical state, he does not receive again the order which he had already.
The Reply to the Third Objection is the same as to the First.
Source: Summa Theologica (New Advent)