The human body can move external bodies, and arrange them in a variety of ways.
PROP.XIV.

The human mind is capable of perceiving a great number of things, and is so in proportion as its body is capable of receiving a great number of impressions.
Proof .-- The human body (by Post.iii.and vi.) is affected in very many ways by external bodies, and is capable in very many ways of affecting external bodies.

But (II.

xii.) the human mind must perceive all that takes place in the human body; the human mind is, therefore, capable of perceiving a great number of things, and is so in proportion, &c.

Q.E.D.
PROP.XV.