By Stewart McCoy

Discovering what to say

This is the second post in a series about using rhetorical principles to develop effective communication in your web project. If you missed the introduction, be sure to read Rhetoric is the New GridIn this post I explain the rhetorical principle of invention. Originally posted on

At the beginning of any web project, it’s important to decide what you’re trying to communicate. Considered communication is the foundation of success. Because to varying degrees, you’re always encouraging people to agree or disagree with your perspective, whether negotiating a statement of work and project budget, marketing your client services or commercial products, or choosing a place for lunch. Critically considering what types of statements you make will ensure you communicate successfully more frequently.

That’s where the rhetorical principle of invention comes in—it’s the method of discovery that will help you decide what type of statement you should make when writing various pieces of content. Aristotle defined invention as “discovering the best available means of persuasion.”

Invention consists of common categories that are useful for brainstorming about what to say. These common categories are referred to as topics of invention. They include:

  • Definition
  • Comparison/Contrast
  • Relationship
  • Circumstances
  • Testimony

To demonstrate how the topics of invention apply to the web, I’ll examine product pages for the Amazon Kindle and Nike + iPod Sport Kit (as sold at Apple).


A definition, by definition, is a statement of meaning. There are many figures of definition, which are different ways to make a defining statement.

Figure 1. The product page for the Amazon Kindle begins with two definitions. The first is descriptive of the purpose and form of the device; the second positions the Kindle against a larger product group, defining the device as the bestseller on the Amazon market.

Definition is arguably the most common mode of communication. We can’t talk about the details of a subject without first establishing meaning and context. For people coming to Amazon to learn more about the Kindle, the product page begins with a definition. We are told that the Kindle is a reading device, is Wi-Fi capable, has a 6-inch screen, and has some fancy “New E Ink Pearl Technology”, which we anticipate will be further defined somewhere on the product page. What’s more, Amazon provides us with a second bit of definition that contextualizes the product: the Kindle is the “#1 bestseller” among all products on the Amazon market. Considering Amazon’s extensive product catalog, that’s an impressive statement that adds an important aspect to Amazon’s definition of the Kindle.

Figure 2. The product page for the Nike + iPod Sport Kit provides extensive definition the device, including concise instructions, and lists for product components, requirements, and specifications.

Like Amazon, Apple’s product page for the Nike + iPod Sport Kit employees multiple methods of definition. Potential consumer concerns regarding what’s included, what’s required, and how it works are all addressed. I’ll address how Apple handles undefined aspects of the product in the section on the topic of circumstances.


Comparison and contrast, like definition, is a basic mode of communication; we need to discuss similarities and differences between things in order to emphasize the uniqueness of a subject.

Figure 3. Amazon offers multiple versions of the Kindle. The product page offers a comparison matrix to help shoppers decide which device is most suited to their needs.

Amazon sells multiple versions of the Kindle. To help shoppers evaluate the various versions of the product, they offer a matrix that compares the feature sets of each device. Maybe you’d initially prefer the 9.7-inch screen of the Kindle DX, but after further comparison, you’d rather have the 1-month battery life and Wi-Fi capability of the Kindle 3G + Wi-Fi.

Figure 4. At the top of the Kindle product page, Amazon recognizes that shoppers might need help choosing among the various versions of the device. The solution is a pop-up that contrasts the Kindle Wi-Fi versus the Kindle 3G.


It’s important to remember that the topics of invention are like a toolbox; you won’t use every tool for every project. The topic of relationship is concerned with issues like cause and effect, antecedent and consequence, contraries, and contradictions. Typically, product pages have no need for a content type that focuses on cause and effect. The topic of relationship is more appropriately used in, say, an essay on thecauses and effects of the poor reading experience on current digital books.


Product pages rely strategically on the topic of testimony, which helps lend credibility to marketing claims and reassures shoppers they are getting a good deal.

Figure 5. Testimonials from people like you and me carry a lot of weight and often guide our purchasing decisions.

The customer review is perhaps the mightiest testimonial for a consumer product. Reviews made by people like you and me provide a helpful overview of how real consumers feel about their purchases, giving us more confidence in our purchasing decisions.

Testimonials are not just for product pages. Testimonials are about appealing to authority and persuading people to your side of an argument. When you cite a Forrester study, Nielsen Ratings, or Jakob Nielsen on usability, you are persuading your audience by making an appeal to credible public figures.

Besides appealing to authority, other methods of testimony include appealing to:

  • witnesses
  • documents
  • law
  • precedent
  • maxims or proverbs
  • rumors
  • oaths
  • the supernatural


What can you do with a Kindle? The topic of circumstances is about the possible and impossible, and the past and future. Circumstances account for the qualities and conditions of the subject.

Figure 6. Amazon highlights the possible: reading in bright sunlight, downloading books in 60 seconds, and choosing from 810,000 books. And with Whispersync, you can access your Kindle content across multiple devices.

There are plenty of circumstances in which you might want to access your Kindle content from other devices. A persuasive selling point is Whispersync, which allows you to access your Kindle content from your notebook, Android device, BlackBerry, iOS device, or Windows 7 device.

Figure 7. For circumstances not accounted for by its own product page, Apple provides a platform for customers to ask questions and share answers with its community.

Apple recognizes the difficulty of accounting for all possibilities on its product page. Their smart solution is community-driven Q&A that allows people to ask and get answers to the most nuanced questions. This solution relieves Apple of the burden of accounting for all conditions and qualities of its product, and allows circumstances to be addressed only when necessary.

Use the Right Tool for the Job

The topics of invention are methods for communicating effectively with your audience. Sometimes you’ll need to define your terms. Sometimes you’ll want to emphasize the uniqueness and utility of your subject through the topic of comparison. All of the time you should think strategically about the types of statements needed to communicate effectively with your audience.

The third post in this series will focus on the principle of arrangement, which concerns methods for organizing effective communication.

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