Objection 1. It would seem that this sacrament has no matter. Because in every sacrament that has a matter the power that works in the sacrament is in the matter. But in the material objects which are used here, such as keys, candlesticks, and so forth, there is not apparently any power of sanctification. Therefore it has no matter.
Objection 2. Further, in this sacrament the fulness of sevenfold grace is conferred, as stated in the text (Sent. iv, D, 24), just as in Confirmation. But the matter of Confirmation requires to be consecrated beforehand. Since then the things which appear to be material in this sacrament are not consecrated beforehand, it would seem that they are not the matter of the sacrament.
Objection 3. Further, in any sacrament that has matter there needs to be contact of matter with the recipient of the sacrament. Now, as some say, it is not essential to this sacrament that there be contact between the aforesaid material objects and the recipient of the sacrament, but only that they be presented to him. Therefore the aforesaid material objects are not the matter of this sacrament.
On the contrary, Every sacrament consists of things and words. Now in any sacrament the thing is the matter. Therefore the things employed in this sacrament are its matter.
Further, more is requisite to dispense the sacraments than to receive them. Yet Baptism, wherein the power is given to receive the sacraments, needs a matter. Therefore order also does, wherein the power is given to dispense them.
I answer that, The matter employed outwardly in the sacraments signifies that the power which works in the sacraments comes entirely from without. Wherefore, since the effect proper to this sacrament, namely the character, is not received through any operation of the one who approaches the sacrament, as was the case in Penance, but comes wholly from without, it is fitting that it should have a matter, yet otherwise than the other sacraments that have matter; because that which is bestowed in the other sacraments comes from God alone, and not from the minister who dispenses the sacrament; whereas that which is conferred in this sacrament, namely the spiritual power, comes also from him who gives the sacrament, as imperfect from perfect power. Hence the efficacy of the other sacraments resides chiefly in the matter which both signifies and contains the divine power through the sanctification applied by the minister; whereas the efficacy of this sacrament resides chiefly with him who dispenses the sacrament. And the matter is employed to show the powers conferred in particular by one who has it completely, rather than to cause power; and this is clear from the fact that the matter is in keeping with the use of power.
This suffices for the Reply to the First Objection.
Reply to Objection 2. It is necessary for the matter to be consecrated in the other sacraments, on account of the power it contains; but it is not so in the case in point.
Reply to Objection 3. If we admit this assertion, the reason for it is clear from what we have said; for since the power of order is received from the minister and not from the matter, the presenting of the matter is more essential to the sacrament than contact therewith. However, the words themselves of the form would seem to indicate that contact with the matter is essential to the sacrament, for it is said: "Receive" this or that.
Source: Summa Theologica (New Advent)