Variety’s the very spice of life,
That gives it all its flavour.
This very famous quote is most often used out of context as positive saying about the need for variety, but Cowper is using it in a negative and ironic way. It occurs in a passage in book two, "The Timepiece," which condemns doing what is selfish and luxurious. "Variety is the spice of life" is a statement apparently coming from the mouths of sycophants, the flatterers who makes their living by convincing people they constantly need the new clothes and fashions that they can supply. As Cowper goes on to say, this kind of variety is vacuous. He says that for the sake of superficial variety, we throw aside elegance in favor of a "monstrous novelty." He argues that domestic joy is ruined by this slavery to fashion's whims; he instead advocates that people think of others before themselves, especially before indulging in the material pleasures of overly fancy clothing and food.
Now stir the fire, and close the shutters fast
This quote occurs at the beginning of the second stanza in book four, called "The Winter Evening." It is the beginning of a domestic passage that extols the simple pleasures of a night in the village home, with the speaker describing a time of being warm, cheerful, and peaceful in domestic bliss. The joy of a happy home is favorably contrasted to a night out at the crowded theater. This evocation of the happiness of a simple life foreshadows the Romantic poets as well as the Victorian sentimental exaltation of the home.
There is in souls a sympathy with sounds
This quote opens book six, "The Winter Walk at Noon." Cowper here means that our minds are pleased by sounds or music that suit(s) our moods and that our moods can be altered by the right sounds. For example, the soft sound of village bells might soothe us: "Falling at intervals upon the ear / In cadence sweet, now dying all away."
Our hearts respond to these sounds; they touch us at a deep emotional level. Moreover, in a move that anticipates the Romantic poets, Cowper asserts that sounds bring back memories (Wordsworth will later assert that returning to the same spot in nature triggers memories). These memories, softened by time and wisdom, can bring us to a mature, nostalgic, sad sweetness as we recognize that we did not appreciate times and people, such as our parents, who are now gone. This is the poetry of sentiment, meant to tug quietly at our heartstrings and encourage us to change.