Catechism of the Summa (11)

 XIV. OF THE VEGETATIVE AND SENSITIVE POWERS

(A)

Are there in the soul divers powers corresponding to the divers acts it produces?

Yes, with the only exception of the first perfection which the soul gives to the body, namely, existence; but it gives this not through some power or faculty, but immediately, of itself 

What powers of the soul give life to the body?

The vegetative powers.

What are these powers?

They are three in number, viz., the power of nutrition, of growth, and of reproduction 

(B)

What faculties of the soul give sense to the body?

The sensitive powers.

What are these powers?

They are twofold: the powers of knowing and the powers of loving.

What are the sensitive powers through which the body knows?

The five external senses 

What are these powers called?

They are called the powers of seeing, hearing, smelling, tasting, and touching.

And the five external senses, what are they called?

They are called sight, hearing, smell, taste, and touch 

Are there also any internal sensitive powers of knowing that do not appear externally?

Yes, they are the common (or central) sense, the imagination, instinct (or estimative sense), and memory

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XV. OF THE MIND AND ITS ACT OF UNDERSTANDING

(A)

Are there any other powers of knowing in man?

Yes, there is another faculty of knowing and it is man's chief power.

What is this chief power of knowing in man called?

It is called his reason or intellect 

Is reason and intellect one and the same power of knowing in man?

Yes 

Why are these two names given to the same power?

It is because in the act of knowing man sometimes understands at a glance as it were without reasoning whereas at other times he must reason 

Is reasoning an act proper to man?

Yes, because of all beings that are, man alone is able to reason, or has need of reasoning.

Is it a perfection in man to be able to reason?

Yes, but it is an imperfection to have need of reasoning.

Why is it a perfection in man to be able to reason?

Because in this wise man can attain to truth; whereas no creature inferior to man, such as animals which are without reason, can do this.

Why is it on the other hand, an imperfection in man to have need of reasoning?

Because in this wise he attains to truth by slow degrees only, and he is thereby liable to err; whereas God and the angels who have no need of reasoning attain to truth straightway without fear of making a mistake.