The three main ways of reasoning are Pathos, Ethos, and Logos. I have tended to see Pathos as inferior to Ethos and Logos because it appears to rely more on emotions than on facts. But does it really ? Are Pathos, Logos, and Ethos equally valid, or are they rankable ?
What the purpose of a speech is? Ideally, no one likes to trick another! Thus, people should ideally try to convey their ideas. This transfer of reasoning is logos: to persuade by logic. Here is my (rhetorical) question: what else is logical? Is "persuading" by touching emotions something really (logically) valid? Of course the fact that an advertisement has nice visual and sonic effects does not mean that the product itself is nice. So, if the purpose of an argument is not to trick the audience but to report the truth and speak objectively, which ideally must be, then logos is the only way that one can persuade another AND be a critical thinker. So, pathos is not an ideal way of persuading people (but if your purpose is not to find the truth but to sell your products then pathos is important for you to make money. It does not mean that your product is really good or not and you do not care. The only thing you want is money.)
Ethos, is a bit different. This is a matter of probability: if person X is authoritative in scientific community, it can be inferred that he has had lots of great (and true) ideas, so the (conditional) probability that person X statement about Y is true this time is high. (of course higher than a highschool student) So, ethos does NOT prove that person X is right this time. It just means that the probability of it is high (but not 1).
As conclusion, if the purpose is proving, the logos is the only way that someone has. Others are not sufficiently logical to prove something. (of course a speaker cannot be his own statement's proof and our emotions - mind, more generally - is not necessarily a representation of reality.)
Ethos, pathos, and logos are a typology of modes of persuasion. They are not mutually exclusive, and in the general case one must invoke all three to be truly persuasive. It's a question of balance and proper usage.
- Pathos builds an emotional connection with the listener, but an excess of pathos alienates others. Pathos without ethos is manipulative; pathos without logos is strident.
- Ethos generates good will and brings the listener to suspend prejudgement, but an excess comes off as snobby or priggish. Ethos without pathos seems hypocritical and supercilious; ethos without logos is rigid and dogmatic.
- Logos is intellectually convincing, but an excess of logos strikes listeners as cold and arrogant. Logos without pathos seems detached and vain; logos without ethos comes across as self-serving, or even delusional (as in conspiracy theories).
If we want to convince someone of something, we need elements of all three.
You might take the time to look at Jurgen Habermas' reasoning modes, which are (in many ways) an updated version of Aristotle's typology. Rather than casting things in terms of persuasion, Habermas sees four different modes of social reasoning, each with its characteristics:
- Teleological action mode: reasoning is focused on the achievement of specific goals. E.g., a company building a bridge will communicate only those things that serve the goal of completing the bridge; a politician intent on getting elected might say or do anything that advances that cause.
- Normative action mode: reasoning is focused on a set of authoritative, pre-given rules and structures. E.g., the training regimes set up for lower-level education, or the 'revealed' teachings of a religious sect.
- Dramaturgical action mode: reasoning is focused on the presentation of an 'authentic' self whose speech acts should be accepted on the merits: e.g., a politician who wants to be seen as a '(wo)man of the people' or 'someone of integrity'; a corporation that wants to present a public face of competence and authority.
- Communicative action mode: reasoning is focused on the comparison and evaluation of ideas, considered separately from the speaker. E.g., academic discourse, or certain kinds of political interactions.
Again, these are not mutually exclusive categories, and the relationship to Aristotle's categories is fairly self-evident. But I find it easier to think of persuasion as a mode of social interaction, and not merely an aspect of an individual's rhetorical style.