Self-pollution is a sin against nature

FOR Fornication and Adultery itself, tho’ heinous Sins, we have Frailty and Nature to plead; but SELF-POLLUTION is a Sin, not only against Nature, but a Sin, that perverts and extinguishes Nature, and he who is guilty of it, is labouring at the Destruction of his Kind, and in a manner strikes at the Creation itself.
—Anonymous, Onania; or, the Heinous Sin of Self-Pollution, and All its Frightful Consequences, Thomas Crouch, London, 1723