William Rosen has a wonderful early example of how too much respect for theory can keep us from making the observations that would eventually prove the theory to be wrong:
(p. 7) Aristotle argued against the existence of a vacuum with unerring, though curiously inelegant, logic. His primary argument ran something like this:
1. If empty space can be measured, then it must have dimension.
2. If it has dimension, then it must be a body (this is something of a tautology: by Aristotelian definition, bodies are things that have dimension).
3. Therefore, anything moving into such a previously empty space would he occupying the same space simultaneously, and two bodies cannot do so.
More persuasive was the argument that a void is unnecessary, that since the fundamental character of an object consists of those measurable dimensions, then a void with the same dimensions as the cup, or horse, or ship occupying it is no different from the object. One, therefore, is redundant, and since the object cannot be superfluous, the void must be.
It takes millennia to recover from that sort of unassailable logic, temptingly similar to that used in Monty Python and the Holy GraiI to demonstrate that if a woman weighs as much as a duck, she is a witch. Aristotle’s blind spot regarding the existence of a void would be inherited by a hundred generations of his adherents. Those who read the work of Heron did so through an Aristotelian scrim on which was printed, in metaphorical letters twenty feet high: NATURE ABHORS A VACUUM.
Rosen, William. The Most Powerful Idea in the World: A Story of Steam, Industry, and Invention. New York: Random House, 2010.
(Note: italics in original.)