Ethos, pathos and logos are three forms of persuasion or argument first articulated by the Greek philosopher Aristotle. Ethos appeals to ethics, pathos to sentiment or emotions and logos to logic.
An appeal to ethos relies on the credibility, competency and reputation of the person making the argument. A person considered an authority on the subject he is speaking about would make an argument of this nature. The argument primarily rests on trusting the opinion or analysis of an authority or expert rather than laying out direct evidence and proof that anyone can follow in the argument.
An appeal to pathos is an emotional argument. Arguments of this nature may target common sentiment, shared cultural values or be structured to manipulate and provoke a direct emotional response. The person making the argument seeks to make the listener identify with them.
An appeal to logos is a logical argument. The credibility of the argument rests on its internal consistency and structure, as well as the evidence presented in support of it. Logical arguments divide into inductive or deductive types.
An argument can be of only one of these styles, but Aristotle believed that an effective argument needed a blend of all three qualities.