The Souls Testimony by Tertullian
Chapter III. But when we say that there are demons -- as though√†
But when we say that there are demons -- as though, in the simple fact that we alone expel them from the men's bodies, we did not also prove their existence -- some disciple of Chrysippus begins to curl the lip. Yet thy curses sufficiently attest that there are such beings, and that they are objects of thy strong dislike. As what comes to thee as a fit expression of thy strong hatred of him, thou callest the man a d√¶mon who annoys thee with his filthiness, or malice, or insolence, or any other vice which we ascribe to evil spirits. In expressing vexation, contempt, or abhorrence, thou hast Satan constantly upon thy lips; the very same we hold to be the angel of evil, the source of error, the corrupter of the whole world, by whom in the beginning man was entrapped into breaking the commandment of God. And (the man) being given over to death on account of his sin, the entire human race, tainted in their descent from him, were made a channel for transmitting his condemnation. Thou seest, then, thy destroyer; and though he is fully known only to Christians, or to whatever sect confesses the Lord, yet, even thou hast some acquaintance with him while yet thou abhorrest him!