The spontaneous and instinctive force within the poet is nature. The rising sun, the "blossoms of the mountain ash" on the hillside, and the grass are all parts of nature, as is "the friend I am happy with." The "real poems" are inside man himself. These "poems of the privacy of the night" are sexual. Love and sexual passion and the human body are poetry. Man is compared to "the hairy wild-bee" that "gripes the full-grown lady-flower, curves upon her with amorous firm legs." All things are involved in this sexual feeling, nature and man alike. The young man who "wakes deep at night" with "the strange half-welcome pangs" is ashamed and angry. But why should man, who is just one part of this process, think himself indecent when birds and animals do not? Paternity and maternity are chaste. Therefore the poet is proud of the "Adamic" in him (his sexual heritage) and has sworn "the oath of procreation" so that he may "produce boys to fill my place when I am through."
The central idea of the poem is contained in the first line: "Spontaneous me, Nature." The free, uninhibited sexual passion within man is indeed natural. Whitman presents two aspects of nature. The human aspect is shown in "the arm of my friend hanging idly over my shoulder" and in "two sleepers at night lying close together as they sleep." The non-human aspect is exemplified in the "hillside whiten'd with blossoms," "the hairy wild-bee," "the wet of woods," and "the dead leaf." Whitman includes all the senses of man, although the emphasis is primarily on the sense of touch.
The poet has taken a vow of procreation. He is eager to give full and free play to his instincts and desires. In this he plays the part of an Adamic man. The sexual images follow each other naturally — the wet of wood, the walnut trunk, the apples — in keeping with the stream-of-consciousness of the poem itself. Thus the phallic is linked with the poetic and the spiritual.
Whitman, in presenting his images, makes use of many equivalents. Objects of nature and of human life are simultaneously presented to show the poet's idea of nature within him. The cluster of images reinforces the idea and the title of the poem. (The poem was originally entitled "Bunch," which expressed the idea of the cluster of images.)