The third historical thinking skill focuses our attention on using evidence to make historical arguments. The word argument reminds us that any attempt to explain the past requires interpretation, since our understanding of the past is limited. Arguing means making a logical — rather than an emotional — case for your interpretation of a particular historical question or controversy. To be convincing, your interpretation has to include supporting evidence. This evidence consists of information you have gathered from primary sources, which are materials produced during the period being studied as well as from existing historical studies, which are called secondary sources.

Historical Argumentation

Historians make arguments about what life was like in the past, how or why things changed, and why those changes matter. Their arguments are informed by their deep knowledge about the subject and careful reading of primary and secondary sources. But because evidence from the past is often incomplete or difficult to understand, historians inevitably make inferences to fill the gaps in their knowledge. Not all historians make the same inferences, so there are a variety of interpretations of most historical events.

For example, all scholars agree that the growth of industry first in England and then elsewhere in the eighteenth and nineteenth centuries was a major historical development. It was so important, in fact, that we call it a revolution: the Industrial Revolution. But historians disagree about the most significant causes for the way industry developed. Some highlight England’s river-accessible coal deposits, which provided a source of power far greater than human or animal power. Others point to the English culture of innovation, in which artisans and inventors read scientific works and looked for solutions to practical problems. Still others emphasize the role of England’s overseas colonies, which provided raw materials and markets for manufactured products.

To develop this historical thinking skill, ask yourself how historians think they know what they know about a particular event. What evidence do they provide? Does their language suggest hesitancy or uncertainty about their interpretation? Do they offer alternative explanations?

Appropriate Use of Relevant Historical Evidence

Historians make arguments about the past based on primary-source evidence. As mentioned earlier, a primary source is something produced in the era under investigation. In contrast, a secondary source, also called a secondary interpretation or a secondary work, is something about the era under investigation created after the fact. It is usually the result of scholarly research of primary sources, or a distillation of such research. The narrative sections of this textbook, for example, are secondary sources, as are most published history works, biographies, and encyclopedias. Sometimes a source can be both primary and secondary. Former British prime minister Winston Churchill’s history of World War II is a primary source, because he was directly involved in some of the events he describes, and also a secondary source, because he uses a variety of historical sources to tell the story of events during the war in which he was not directly involved.

Traditionally, primary sources have consisted overwhelmingly of written sources. In fact, some historians referred to any time before writing as “prehistoric.” In the last few decades, however, historians have increasingly moved beyond relying exclusively on written primary sources by turning to visual sources — paintings, photographs, architecture, artifacts, and so on — and evidence from other fields of knowledge. They even use evidence contained within the human body, such as DNA. For example, by using scientific and medical information, historians have come to see the historical role of diseases, such as the Black Death, which killed about one-third of the European population over just a few years in the middle of the fourteenth century. Since no historian can be an expert in every field, historians increasingly make use of the secondary sources produced by scholars in other fields, including archaeology, art history, biology, and chemistry.

In assessing primary sources, you need to begin with a careful examination of the source itself. But understanding evidence requires more. Primary sources are creations from a particular time and place, so you also have to consider the information that you know or can find out about the broader conditions in which the source was created — that is, the context of the source. Primary sources are created by a specific individual or group, called the maker, or, in the case of written sources, the author. Even if they are eyewitnesses, people construct different accounts of the same event, which are shaped by their ideas, attitudes, and beliefs, often termed their perspective or point of view. Primary sources are also often created for someone else, so determining the purpose and intended audience of a source is essential to your understanding of it.