How often have you had a discussion with someone where a misunderstanding was instantly cleared up by the words, “Oh! You meant _____! Fill in the blank with just about any concept. The point here is how the other person’s perspective was immediately understood with the clarification on what was meant. I have both had and observed this same moment of clarity regarding the topic of evolution.
Considering that the topic of evolution is so … heated, it would be good idea to get our definitions from a reputable, authoritative source. And to be clear, this will not be an illegitimate appeal to authority. There are legitimate appeals to authority. As Wesley Salmon states,
There are correct uses of authority as well as incorrect ones. It would be a sophomoric mistake to suppose that every appeal to authority is illegitimate, for the proper use of authority plays an indispensable role in the accumulation and application of knowledge. If we were to reject every appeal to authority, we would have to maintain, for example, that no one is ever justified in accepting the judgment of a medical expert concerning an illness. Instead, one would have to become a medical expert oneself, and one would face the impossible task of doing so without relying on the results of any other investigators.1 (screenshot_1 & 2)
The particular authority that is to be cited here is very prominent in the scientific community related to the topic of evolution. His name is Francisco J. Ayala (wiki). Here is the link to his faculty page at University of California, Irvine, where you can see a detailed list of his published books and his journal articles. Among his numerous awards and honorary degrees, he was also awarded the National Medal of Science in 2001. Surprisingly, few people outside of the scientific community are aware of his name.
“The theory of evolution”, as defined by Dr. Ayala, “makes statements about three different, though related, issues:
(1) The fact of evolution, that is, that organisms are related by common descent;
(2) Evolutionary history—the details of when lineages split from one another and of the changes that occurred in each lineage;
(3) The mechanisms or processes by which evolutionary change occurs.”2 (screenshot)
Further down the same page, Ayala then provides more clarity on these definitions. Regarding the first issue he says that it “is the most fundamental and the one established with utmost certainty.” It is this definition, he says, that “is implied when biologists say that evolution is a ‘fact’…”
Ayala adds that regarding “The second and third issues—seeking to ascertain evolutionary history, as well as to explain how and why evolution takes place—are matters of active scientific investigation.” (emphasis mine).
Many of the discussions I have seen and been a part of have not done a very good job of clarifying definitions. And since I started using these definitions in my discussions, it has helped prevent some of the confusion and misunderstandings. Hopefully these definitions from a very prominent biologist will help clear up some of the confusion and misunderstandings in your discussions as well.