Reply Obj. 2: In the passions of the sensitive appetite there may be distinguished a certain material element—namely, the bodily change—and a certain formal element, which is on the part of the appetite.
 Thomas Aquinas, Summa Theologica (1274). copy citation

add
Author Thomas Aquinas
Source Summa Theologica
Topic passion change
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“Love, therefore, and joy and delight are passions; in so far as they denote acts of the intellective appetite, they are not passions. It is in this latter sense that they are in God. Hence the Philosopher says (Ethic. vii) : "God rejoices by an operation that is one and simple," and for the same reason He loves without passion.
Reply Obj. 2: In the passions of the sensitive appetite there may be distinguished a certain material element—namely, the bodily change—and a certain formal element, which is on the part of the appetite. Thus in anger, as the Philosopher says (De Anima iii, 15, 63, 64) , the material element is the kindling of the blood about the heart; but the formal, the appetite for revenge. Again, as regards the formal element of certain passions a certain imperfection is implied, as in desire, which is of the good we have not, and in sorrow, which is about the evil we have.” source