Evolution a fact of science? Part One

In the media, textbooks and scientific blogs the occurrence of evolution has become a "fact".
The definition of the word evolution has also taken on two different meaning that are not equal. Evolution can be used in the sense of change in a species by natural selection. This is often referred to as microevolution and is accepted by evolutionists and creationist alike as good observational science. This type of evolution allows change within groups but not between groups.
The other meaning of evolution involves the idea that all organisms on earth share a common ancestor by descent with modification. This idea is commonly referred to as macroevolution.
The definitions are often used interchangeable. Typical, textbooks show that new species can form-evolution has occurred- so they argue that is obvious that evolution, in the molecules-to-man sense, must have occurred. The problem is that just because natural selection and speciation have occurred (and there is strong evidence to support such claims) the claim that all life has evolved from a common ancestor is based on many assumptions that cannot be proven.
People believe the ideas of the evolutionary development of life on earth for many reasons: it is all that they have been taught and exposed to, they believe the evidence supports evolution, they do want want to be lumped with people who do not believe in evolution and are often considered to be less intelligent, evolution has the stamp of approval from real scientists and evolutionary history allows people to reject the idea of God and legitimize their own immorality. Evaluating the presuppositions behind belief in evolution makes for a much more productive discussion. Two intelligent people can arrive at different conclusions using the same evidence; so their starting assumptions is the most important issue in discussing historical science.