Building a Critical Mass

Throughout Part 4 (Chapters 17, 18, 19, 20, 21, and 22), “Research and Arguments,” we’ve stressed the need to discover as much evidence as possible in support of your claim and to read and understand it as thoroughly as you can. If you can find only one or two pieces of evidence — only one or two reasons or illustrations to back up your thesis — then you may be on unsteady ground. Although there’s no definite way of saying just how much evidence is enough, you should build toward a critical mass by having several pieces of evidence all pulling in the direction of your claim. Begin by putting Rheingold’s triangulation into practice: find at least three credible sources that support your point.

And remember that circumstantial evidence (that is, indirect evidence that suggests that something occurred but doesn’t prove it directly) may not be enough if it is the only evidence that you have. In the infamous case of Jack the Ripper, the murderer who plagued London’s East End in 1888, nothing but circumstantial evidence ever surfaced and hence no one was charged with or convicted of the crimes. In 2007, however, amateur detective Russell Edwards bought a shawl at auction — a shawl found at one of the murder sites. After consulting with a number of scientific experts and using DNA evidence, Edwards identified Jack the Ripper as Aaron Kosminski, who eventually died in an asylum.

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If your evidence for a claim relies solely on circumstantial evidence, on personal experience, or on one major example, you should extend your search for additional sources and good reasons to back up your claim — or modify the argument. Your initial position may simply have been wrong.