No one who is capable of self-control is necessarily vicious;
No one who is capable of self-control is necessarily vicious
 John Stuart Mill, A System Of Logic, Ratiocinative And Inductive (1843). copy citation

Context

“All animals are mortal; All men/Some men/Socrates are animals; therefore All men/Some men/Socrates are mortal. To prove a negative, the argument must be capable of being expressed in this form: No one who is capable of self-control is necessarily vicious; No one who is capable of self-control is necessarily vicious; All negroes/Some negroes/Mr. A's negro are capable of self-control; therefore No negroes are/Some negroes are not/Mr. A's negro is not necessarily vicious. Though all ratiocination admits of being thrown into one or the other of these forms, and sometimes gains considerably by the transformation, both in clearness and in the obviousness of its consequence;” source