"Molecular biology is an experimental rather than a theoretical science.
Whether we want to know why globin genes are expressed only in red blood
cells or why the fruit fly has a segmented body, we expect every theory to
be tested experimentally and ultimately proved or disproved. We can afford
to have such high expectations of molecular biology because the living
system that we study can be manipulated experimentally to test each theory."
-Watson, James D. et al. 1987. Molecular Biology of the Gene. The Benjamin
Cummings Publishing Company. pp1-1163