In the book of psalms we read, "The sun knows the hour of its setting." (Ps 104:9). Today we would say that the earth knows the time of its rotation. Implied in these statements is the idea of knowledge and order in creatures.
There is a marvelous order in nature in its design and function which gives it the unity of being. The moon moves around with its relationship to the earth; the apples hang on the tree because its stem is strong enough to counterbalance the pull of gravity; the butterfly is light enough to be able to feed on the pollen of a fragile flower; each leaf falls to the ground in a certain way due to the pull of gravity and the uplift provided by the air; the frozen snow hangs on slender branches because the snow flakes froze there. In walking, man must place one foot before another or he will fall over. In all of nature we see an order based on relationships.
Whatever man produces must have an order or it will not come to be or function. A vase must have a certain shape to hold water. If we write an e-mail address without its proper dot, it will not be delivered. If the musician fails to follow the proper order of the notes, the music will sound discordant. Whatever man makes is designed in his mind but this design must conform to the external laws of nature to become a work of art.
Order comes about because relationships are being established between differing realities and this order is due to the tendency of each creature to find in relationships. This is the work of Divine intelligence which gives being to all creatures with their abilities and tendencies toward relationships. Order is the foundation of peace which can be defined as harmonious relationships among creatures. "Peace, in the final sense, is the calm that comes from order." (Augustine, City of God, Bk. XIX, ch. 13)