Aristotle has just finished describing where someone might obtain the propositions necessary to argue a position from. Now he is going to continue his discussion on the tools of argument by dividing the first tool – propositions – into three based on content. He does this in Topics, Book 1.
Of propositions and problems there are—to comprehend thematter in outline—three divisions; for some are ethical propositions, some are on natural science, while some are logical. Propositions such as the following are ethical, e.g. ‘Ought one rather to obey one’s parents or the laws, if they disagree?’; such as this are logical, e.g. ‘Is the knowledge of opposites the same or not?’; while such as this are on natural science, e.g. ‘Is the universe eternal or not?’ Likewise also with problems. The nature of each of the aforesaid kinds of proposition is not easily rendered in a definition, but we have to try to recognize each of them by means of the familiarity attained through induction, examining them in the light of the illustrations given above.
Aristotle has hinted at this sort of division earlier in his discussion on dialectical problems. There are three kinds of things we could argue about. Some propositions and problems are ethical, others are matters of the world and still others are logical. The proposition ‘Should we obey our parents rather than the law if they disagree’ is ethical. Such a proposition is about choice. The problem ‘Is knowledge of opposites the same or not’ is logical. The problem ‘Is the universe eternal or not’ is about the world. Such a proposition is about knowledge. We cannot always tell right away which category a proposition or problem belongs to. Nor can we define the categories better, since they cannot be easily defined. We have to use induction and compare particular arguments with the examples here. Practice will make it easier to determine which category a proposition or problem belongs to.
This division into physics, logic and ethics would continue for centuries. Aristotle is the first philosopher known to make this distinction – but it was another philosopher who applied it to philosophy as a whole rather than propositions and problems. In any case, the division of propositions and problems by content is a good idea – especially when arguing.
Next, Aristotle will discuss how to use propositions in arguments.