“The practical mind that loves facts and distrusts theory should acquire some patience and pause a while over the theory of facts. There may at first be reluctance to face the question, What is fact? Yet, if facts are unyielding absolutes, it ought not to prove too difficult to show what a fact is. Let us try.
Is it a fact that the Earth is round? In the Middle Ages the common people thought it was flat. Since then, evidence has accumulated (considerable evidence was known to astronomers during the Middle Ages) and has been disseminated, until today everyone takes it as a fact that the Earth is round. But strictly, is it the Earth’s roundness that is a fact, or is it the items of evidence that are facts on which the conclusion of the Earth’s roundness rests? For example, the shadow of the Earth on the Moon during a lunar eclipse has a round edge: Perhaps this is a fact, and the roundness of the Earth is a theory. Of course, it is not a fact that the Earth is a sphere: it is flattened at the poles. But if it is not a fact that the Earth is perfectly round (spherical), what is the fact? Is it a fact that the Earth is an oblate spheroid? But this term embraces a variety of forms and proportions. Which form exactly is the absolute unchangeable fact? -though science does not pride itself on sticking to facts such as this.
Above, it was said that the shadow of the Earth in a lunar eclipse is a fact-on which the roundness of the Earth is erected as a theory. But is even the shadow a fact? Is it not rather the fact that a certain darkness on the Moon has around edge, and is it not a theory that this darkness is the shadow of the Earth?
This type of analysis seems to lead to the conclusion that all, or at least many, alleged facts are theories developed out of simpler items of perception. The problem naturally a rises whether there is any fact that is not a theory. Is there anything seen directly as what it is? No doubt many people in Atlantic City on a fine summer’s day have seen an airplane high in the air pursuing an even course; and as they have watched the plane so high and so small, it has flapped its wings and dived to get a fish. Was it a fact that it was an airplane, or was this a theory about a small object in the sky? What is a fact?”