1.4 Gathering and Evaluating Evidence

No thesis, however intriguing, can be persuasively communicated to a skeptical reader without the support of compelling evidenceDetails, facts, authoritative citations, illuminating analogies, and examples that support a claim.. Evidence consists of details, facts, authoritative citations, illuminating analogies, and examples. As readers, we are convinced by the presentation of evidence that is as follows:

Imagine you are writing an essay on the ethics of cooking lobsters by putting them, while still alive, into a pot of boiling water. In your research, you have discovered the following sentence in an argument defending the practice: “Lobsters do not feel pain because they do not have a cerebral cortex, which in humans is the area of the brain that gives the experience of pain.”

As a critical reader and writer, you will question this evidence. And while in all practicality we cannot check every fact offered by every writer, we can reserve judgment until we find ourselves satisfied. Is the foregoing sentence regarding the lobster’s lack of a cerebral cortex accurate? Without fact checking, we might be inclined to say “probably.” Is it specific? Yes. Is it relevant? Here, we may hesitate. Is the cerebral cortex, or lack thereof, the only determinant of an animal’s experience of pain? Perhaps the absence of a cerebral cortex in lobsters is irrelevant with regard to their experience of pain. Careful readers will question the conclusion drawn from the evidence even if the evidence is accurate.

Sometimes writers must gauge not only whether the evidence they have supplied is accurate, specific, and relevant but also whether it is sufficient. The evidence offered in the previous example would be insufficient to win an argument about the ethics of boiling live lobsters. However, combined with other facts and examples, the evidence could be effective. The evidence might be derived from expert opinion, well-chosen examples, logic, or informally conducted interviews.