Answer:
Definitions
Argument is the attempt to prove a point using evidence and reasoning.
This handout discusses evidence. I cover reasoning in a separate handout.
A claim is a statement about something, which could, in theory, be supported with evidence. It is an assertion about the way things are, or were, or will be, or should be. Claims are, almost by definition, controversial, in the sense that not everyone agrees with them. That is why they require evidence.
Evidence is the concrete facts used to support a claim. Ideally, evidence is something everyone agrees on, or something that anyone could, with sufficient training and equipment, verify for themselves.
Evidence comes in many types, which I discuss in detail here.
At its most basic, evidence is something that can be perceived with the senses. A great deal of scientific evidence is observable phenomena, like the change in color when two chemicals are mixed in an experiment, or the light emitted by a distant star, or the structure of bones in a fossil. In some cases, though, what you’re observing is very removed from the claim. For example, if I say “Einstein said that space is curved” as a fact to support my claim, the observable fact is the written record of what Einstein said, not a physical phenomenon that relates directly to my claim.
There is no clear-cut line between a claim and a “fact.” Things that are facts in one context might be claims in another. For example, “the earth orbits the sun” was once a claim (i.e. an unproven or controversial assertion), but now nearly everyone accepts it as a fact. Many arguments begin by treating something as a claim, try to prove it, and then, once they have proved it to the author’s satisfaction, treat it as a fact to be used as evidence to support some new claim. However, in well-constructed arguments you can usually distinguish pretty easily between the claim and the facts used to support it. Generally speaking, successful arguments will rely on well-established facts for their evidence, at least in the beginning. If it’s hard to tell the difference between the claims and the facts, this might be one sign of a badly constructed argument, one that relies on faulty evidence or reasoning to support its claims.
