This is in response to some issues brought up in other threads, regarding faith, God and the scientific appraoch to knowledge.
Rooster wrote: "prof, evolution is not a "fact". It is not "true". It is called a theory."
To quote an on-line encyclopaedia: "Most non-scientists are unaware that what scientists call "theories" are what most people call "facts".
I've been talking about "facts" and "theories" in the scientific sense. Science does not claim to offer absolute "truth" or perfect confidence. Therefore, all knowledge is provisional, including what we think are "facts." For instance, like most humans throughout our history you may assume it to be a fact that the objects you can touch, like your desk, are solid objects. But that notion is disproved by an introduction to atomic physics. All sorts of things that seemed factual throughout history have been proven otherwise. Facts themselves - even ones we apparently can observe at will - merely hold a high confidence level because they survive our attempts to verify (or falsify) them. And there are all sorts of facts that are not repeatedly observable, which are in essence historical - previously observed passing of asteroids near earth, volcanoe explosions that destroyed towns, plague epidemics etc...the list is endless. But they remain facts because of the preponderance of evidence, and because we observe natural processes that can logically support the idea they happened. (Which is why "historical" reports of supernatural events are not taken as facts because, among other good reasons, there is no currently observable mechanism to lend confidence those events could have happened). Nor, by the way, does a phenomenon held to be factual by science have to be directly observed - it may be inferred. Think mountain formation, gravity, atoms, meteor impacts etc. All scientific facts.
Likewise with scientific theories. The same type of confidence-level-testing that puts something in the realm of "fact" applies to putting scientific theories into the realm of "proven" or "fact." There is the data (facts), and there is the premise of how that data is related (theory). If the theory survives repeated attempts to verify or falsify the premise of how the data are related, we may take it as "fact" the data are related in that way (the Theory is scientifically "proven"). So, a theory may be an explanation for a set of facts, yet after enough testing the theory itself may be taken as factual - especially in the case of extremely robust, fruitful theories like Evolution, Electromagnetism or Relativity.
For evolutionary theory the data - the set of facts or evidence - are found in fossils, genetics, anthropology, comparative anatomy, biochemistry, cladistics, etc. The theory of evolution suggests a relationship between the set of facts. That relationship is tested for, by lab tests that show the basic evolutionary mechanism works, and by searching for evidence of common genetic and phenotype descent in the natural world (via fossils, comparative anatomy, genetic evidence etc.) And the relationships suggested by the theory are indeed found in abundance.
So in evolution we have a theory that is a logical extrapolation from observable processes, it provides an explanatory and predictive mechanism, along with an enormous amount of observed evidence to support that the earth's biology is related in the way evolutionary theory says it should be. Hence, the theory has long ago reached the status of "proven," and is taken by science to be a fact.