All sensuality is one, though it takes many forms; all purity is one. It is the same whether a man eat, or drink, or cohabit, or sleep sensually. They are but one appetite, and we only need to see a person do any one of these things to know how great a sensuallist he is. The impure can neither stand nor sit with purity. When the reptile is attacked at the mouth of his burrow, he shows himself at another. If you would be chaste, you must be temperate. What is chastity? How shall a man know if he is chaste? He shall not know it. We have heard of this virtue, but we know not what it is. We speak conformably to the rumor which we have heard. From exertion come wisdom and purity; from sloth, ignorance and sensuality. In the student, sensuality is a sluggish habit of mind. An unclean person is universally a slothful one, one who sits by a stove, whom the sun shines on prostrate, who reposes without being fatigued. If you would avoid uncleanness and all the sins, work earnestly, though it be cleaning a stable.
From “Higher Laws,” Walden, 1854. (Quoted in Classical Rhetoric for the Modern Student by Corbett and Connors, 106.)