Forms of evidence

Most of the examples we've seen in this lesson have given some indication of where the evidence came from:

• Whose personal experience?
• What direct observations?
• Which systematic research studies?
• Which experts?
• What group of survey respondents?

Sometimes, providing your sources is critically important.

For example, academic researchers in journal articles will cite the source (sometimes multiple sources) for every single statement.

But there are many everyday situations in which explaining the evidence that backs up each of your statements would bog the entire argument down and prevent you from getting to your point.

A good example is history and science books written for lay audiences.

For example, Inventing Human Rights is a history book that makes a causal argument about where the concept of human rights came from and how they were enshrined in laws.

As part of that argument, this snippet recounts political debates that followed the storming of the Bastille prison in Paris, in 1789:

This snippet makes a variety of statements that serve as evidence for a larger point, which is that during this period, a declaration of universal rights was much contested and nearly didn't happen.

But how do we know any of those statements are true?

• Did the king withdraw his troops?
• Were deputies debating whether they needed a declaration of rights?
• Did some people really believe that monarchical authority only needed repairs?

Lynn Hunt, the writer, could provide the evidence for every statement in the book, but it would be 12,000 pages long and annoy anyone who already knew what happened during the French Revolution.

So, instead, Hunt assumes all these statements are accepted facts.

Accepted facts are statements that are supported by large bodies of evidence that many experts have evaluated and argued about until they've reached a consensus.

We see the same thing in popular science writing.

In this snippet, John Carey, describes the peculiar weakness of gravity compared to subatomic forces like electromagnetism as evidence to support a claim that a certain poem is about gravity:

Again, a number of statements are presented as accepted facts:

• There are four fundamental forces.
• Gravity is the weakest force.

Is any of that true? Could you prove it?

You probably couldn't prove it, and John Carey's not going to spend time proving it either, because so many experts have looked at the evidence supporting those statements that, until further notice, they can be taken as fact.

That's not to say you can't dig into the evidence for yourself!

For instance, let's take one statement from Inventing Human Rights:

What is the evidence for this statement? Did these deputies exist and did they have this debate?

Lynn Hunt, being a professional scholar, provides footnotes to explain her sources:

Some of those references are in French, but one is a history book by Timothy Tackett titled Becoming a Revolutionary: The Deputies of the French National Assembly and the Emergence of a Revolutionary Culture (1789–1790).

If we wanted to know more about these debating deputies we could look up that book and page reference, and find that it is full of dramatic details that support Hunt's account:

Notice how Tackett uses direct quotes because, unlike Hunt, his argument is about what exactly happened in this National Assembly, so he cites observational evidence.

If we wanted to go deeper still, we could look at the sources Tackett says he referred to for his evidence:

Most of these are French manuscripts (some of which Lynn Hunt also used), including the Parliamentary Archives from 1789, which you can find online at the University of Chicago and read for yourself (if you speak French or want to copy-paste into a translator):

Let's look again at that snippet from John Carey, about the four forces:

Are there really only four fundamental forces? Is gravity really the weakest?

To dig deeper, we could look up fundamental forces on Wikipedia:

We could keep digging into how the strength of another force like the weak force is measured, but again we quickly run into evidence that requires a greater level of context and expertise to understand:

What we're seeing here is the way in which evidence slowly gets "packaged up" into accepted facts.

This is the whole process of human scholarship, science, and knowledge production.

• We might begin with personal experiences, which make someone want to collect more observational data.
• They collect data at such a scale that they need to turn it into numbers and statistics, which they then publish as a study.
• Experts evaluate that study and compare it to other studies, and everyone argues, until eventually some kind of consensus conclusion emerges, and that may begin to be treated as a fact (or at least a claim that doesn't need explaining).

To recap

• In contentious issues, it's important to explain exactly where your evidence comes from.
• But other times, particularly in situations where the audience trusts the speaker, like when you're reading a history or science book, there's no need to get bogged down in explaining all the evidence.
• Instead, you can build sections of your argument out of accepted facts.
• However, you can also challenge those facts and investigate the underlying evidence base.
• This process can sometimes involve digging down through several layers of evidence until you find the raw observational data.
• The risk is that when you get down to the bottom, you need a lot of context and expertise to properly understand the data.
• That's because accepted facts (at least on complex issues) have usually been produced through a long process of observation, analysis, and argument.
• That doesn't mean that we can't or shouldn't investigate evidence, but it's worth being aware of the complexities and approaching deeper research with some patience and humility.