Aristotle has just finished discussing the four tools of argument. This continues his discussion of how we will find arguments by discussing the first tool: propositions. He does this in Topics, Book 1.
Propositions should be selected in as many ways as we drew distinctions in regard to the proposition: thus one may choose the opinions held by all or by most men or by the wise, i.e. by all, or most, or the most notable of them if they are not contrary to those that seem to be generally held- and, again, all opinions that are in accordance with the arts. We must make propositions also of the contradictories of opinions contrary to those that seem to be generally held, as was laid down before. It is useful also to make them by selecting not only those opinions that actually are reputable, but also those that are like these, e.g. that the perception of contraries is the same the knowledge of them being so and that we see by admission of something into ourselves, not by an emission- for so it is, too, in the case of the other senses- for in hearing we admit something into ourselves- we do not emit- and we taste in the same way. Likewise also in the other cases. Moreover, all statements that seem to be true in all or in most cases, should be taken as a principle or accepted thesis– for they are posited by those who do not also see what exception there may be. We should select also from the written handbooks of argument, and should draw up sketch-lists of them upon each several kind of subject, putting them down under separate headings, e.g. On Good, or On Life and that On Good should deal with every form of good, beginning with the essence. In the margin, too, one should indicate also the opinions of individual thinkers, e.g. that Empedocles said that the elements of bodies were four- for any one might assent to the saying of some reputable authority.
We should choose propositions from dialectical propositions. When we discussed those we showed that these included opinions held by all people, most people and by experts provided that they are not contrary to most peoples opinion. They also include propositions found in various areas of knowledge, propositions contradicting the contraries of reputable propositions and propositions similar to reputable propositions. For example, perception of contraries is the same because knowledge of contraries is the same. We see by letting something into ourselves, not by putting something into the world. Hearing and the other senses function in this way too. We can also choose propositions that seem to be true in all or most cases because those who agree with them do not see what the exceptions might be. We should also use textbooks and other expert-written books to find arguments on several different subjects such as Goodness and Life. With Good, we would put every different description of good starting with what goodness is. We should also include the opinions of experts. Empedocles, in the time of Aristotle was such an expert. He believed that there were four physical elements. His opinion would be included because some might agree with it.
Next, Aristotle discusses another division of propositions into three categories. This division divides them by subject-content or what they are about.