The Canon of Invention: Key Features Explained

Invention, the first canon of the Five Canons of RhetoricOpens in new window, (also known as “discovery” or “finding something to say”) refers to the process of coming up with arguments suitable to a particular situation.

Invention focuses on the argumentative, persuasive core of rhetoric. AristotleOpens in new window defines invention as “discovering the best available means of persuasion.”

A rhetor (speaker or writer) who is involved in the invention process, would typically considers what the audience might need to know, and assembles the necessary evidence. This involves reflecting on the imaginary audience; say, for example, the subject is healthcare: will the listeners expect a scientific discourse, a partisan policy speech, or ‘Rose Garden rubbish’ commending health-workers?

Invention also involves deciding what is really at issue in a situation where the subject matter of a speech is controversial. Thus, if a politician is accused of misuse of funds, her opponents may say that the allegations cast doubt on her fitness for office; she may react by saying that the charges are ‘politically motivated’ and ‘a distraction from the real issues in this campaign.’ —(Richard Toye, Rhetoric: A very Short Introduction

The Techniques of Invention

The following are assisted techniques that enhances part of the invention process.


Stasis is a series of standard questions that helps rhetors decide, within the process of invention (discovery), what they may themselves believe is fundamentally at stake.

Stasis typically consists of four crucial questions:

  1. question of fact;
  2. question of definition;
  3. question of quality;
  4. question of procedure/jurisdiction — that the rhetor asks oneself when planning an argument.

Take for example, the case of the politician and the questions she may ask herself when preparing a speech in her defence.

  1. Did anything happen? (Question of fact: Yes, a few thousand dollars briefly ended up in the wrong account.)
  2. Was any harm done? (Question of definition: Yes, there was a technical breach of the rules, which I regret, but I returned the money as soon as it was brought to my attention.)
  3. Was the harm done serious? (Question of quality: No, this was a minor infringement that occurred accidentally without any intent to deceive.)
  4. Is this the right place to be discussing this? (Question of procedure/jurisdiction: No, let us wait for the official report into the matter and in the meantime get back to debating the vital questions facing the country.)

Topoi (Topics of Invention)

Another important technique in the invention process, is topoi (topics of invention).

Topics of invention literally means “a series of ways of looking at problems in order to generate arguments.” Aristotle divided these into the “Common” and “Special” topics of invention.

The “common” categories of thought include:

  1. DefinitionOpens in new window (determining how to classify the idea, what its genus/species is);
  2. DivisionOpens in new window (planning and outlining arguments into segments of whole/parts or subject/adjuncts);
  3. ComparisonOpens in new window (contrasting the better and the worse);
  4. Cause & Effect (outlining possible detrimental antecedent & consequences); Circumstances (presenting possible/impossible, past/future fact);
  5. TestimonyOpens in new window (bringing on authorities, witnesses, oaths, etc).

These are more conventional and appropriate to use when brainstormingOpens in new window for thoughts in any argument.

The “special” categories, on the other hand, are relevant and applicable only to each of the three branches of oratory:

  1. Judicial  Opens in new window (justice [right] and injustice [wrong]);
  2. Deliberative  Opens in new window (the good, the unworthy, the advantageous, the disadvantageous);
  3. Epideictic or Ceremonial  Opens in new window (virtue [the noble], vice [the base]).

Again looking at the case of the politician, she may apply the the technique of the topoi or ‘topics of invention’ while trying to organize her thoughts and elaborate her answers to the questions.

For example, considering the topos of comparisonOpens in new window could help her think of arguing that her errors were much less significant than those committed by her opponents or by past occupants of the office for which she is running.

The topos of cause and effect could lead her to argue that her mistakes was caused by the fact that she was distracted by the pressing issues of the day, but that the results of it were at any rate trivial. Of course, her opponents would likely use the identical techniques to come up with radically different arguments.

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