According to St. Thomas Aquinas, God created the diversity of creatures because no single creature can adequately reflect the perfection of God:
“We must say that the distinction and multitude of things come from the intention of the first agent, who is God.
“For He brought things into being in order that His goodness might be communicated to creatures, and be represented by them.
And because His goodness could not be adequately represented by one creature alone, He produced many and diverse creatures, that what was wanting to one in the representation of the divine goodness might be supplied by another.
“For goodness, which in God is simple and uniform, in creatures is manifold and divided and hence the whole universe together participates in the divine goodness more perfectly, and represents it better than any single creature whatever.” (Summa theologiae, I.47.1, emphasis added)
Psalm 19 (18)
1The heavens proclaim the glory of God; and the firmament declare his handiwork.
2Day to day pours forth speech, and night to night declares knowledge.
3There is no speech, nor are there words; their voice is not heard;
4yet their voice goes out through all the earth, and their words to the end of the world. In the heavens he has set a tent for the sun,
5which comes out like a bridegroom from his wedding canopy, and like a strong man runs its course with joy.
6Its rising is from the end of the heavens, and its circuit to the end of them; and nothing is hid from its heat.
7The law of the Lord is perfect, reviving the soul; the decrees of the Lord are sure, making wise the simple;
8the precepts of the Lord are right, rejoicing the heart; the commandment of the Lord is clear, enlightening the eyes;
9the fear of the Lord is pure, enduring forever; the ordinances of the Lord are true and righteous altogether.
10More to be desired are they than gold, even much fine gold; sweeter also than honey, and drippings of the honeycomb.
11Moreover by them is your servant warned; in keeping them there is great reward.
12But who can detect their errors? Clear me from hidden faults.
13Keep back your servant also from the insolent; do not let them have dominion over me. Then I shall be blameless, and innocent of great transgression.
14Let the words of my mouth and the meditation of my heart be acceptable to you, O Lord, my rock and my redeemer.