tual powers; thirdly, the appetitive powers.

Under the first head there are four points of inquiry:

(1) The powers of the soul considered generally;

(2) The various species of the vegetative part;

(3) The exterior senses;

(4) The interior senses.
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FIRST ARTICLE [I, Q. 78, Art. 1]

Whether There Are to Be Distinguished Five Genera of Powers in the
Soul?

Objection 1: It would seem that there are not to be distinguished
five genera of powers in the soul--namely, vegetative, sensitive,
appetitive, locomotive, and intellectual. For the powers of the soul
are called its parts. But only three parts of the soul are commonly
assigned--namely, the vegetative soul, the sensitive soul, and the
rational soul. Therefore there are only three genera of powers in
the soul, and not five.

Obj. 2: Further, the powers of the soul are the principles of its
vital operations. Now, in four ways is a thing said to live. For the
Philosopher says (De Anima ii, 2): "In several ways a thing is said
to live, and even if only one of these is present, the thing is said
to live; as intellect and sense, local movement and rest, and lastly,
movement of decrease and increase due to nourishment." Therefore
there are only four genera of powers of the soul, as the appetitive
is excluded.

Obj. 3: Further, a special kind of soul ought not to be assigned as
regards what is common to all the powers. Now desire is common to
each power of the soul. For sight desires an appropriate visible
object; whence we read (Ecclus. 40:22): "The eye desireth favor and
beauty, but more than these green sown fields." In the same way every
other power desires its appropriate object. Therefore the appetitive
power should not be made a special genus of the powers of the soul.

Obj. 4: Further, the moving principle in animals is sense,
intellect or appetite, as the Philosopher says (De Anima iii, 10).
Therefore the motive power should not be added to the above as a
special genus of soul.

_On the contrary,_ The Philosopher says (De Anima ii, 3), "The powers
are the vegetative, the sensitive, the appetitive, the locomotion, and
the intellectual."

_I answer that,_ There are five genera of powers of the soul, as above
numbered. Of these, three are called souls, and four are called modes
of living. The reason of this diversity lies in the various souls
being distinguished accordingly as the operation of the soul
transcends the operation