The Parable of The Foolish Ichthyologist
I came across an interesting analogy about science and knowledge given by Sir Arthur Eddington, taken from The Philosophy of Physical Science, Ann Arbor Paperbacks, The University of Michigan Press, 1958, p 16.
"Let us suppose that an ichthyologist (the branch of zoology that deals with the study of fishes) is exploring the life of the ocean. He casts a net into the water and brings up a fishy assortment. Surveying his catch, he proceeds in the usual manner of a scientist to systematise what it reveals. He arrives at two generalisations: (1) No sea-creature is less than two inches long.(2) All sea-creatures have gills. These are both true of his catch, and he assumes tentatively that they will remain true however often he repeats it.
In applying this analogy, the catch stands for the body of knowledge which constitutes physical science, and the net for the sensory and intellectual equipment which we use in obtaining it. The casting of the net corresponds to observation; for knowledge which has not been or could not be obtained by observation is not admitted into physical science. An onlooker may object that the first generalisation is wrong. "There are plenty of sea-creatures under two inches long, only your net is not adapted to catch them." The icthyologist dismisses this objection contemptuously. "Anything uncatchable by my net is ipso facto outside the scope of icthyological knowledge. In short, "what my net can't catch isn't fish." Or--to translate the analogy--"If you are not simply guessing, you are claiming a knowledge of the physical universe discovered in some other way than by the methods of physical science, and admittedly unverifiable by such methods. You are a metaphysician. Bah!"
The point of Sir Eddington's little parable? Be sure you go fishing with the right net when you are looking for truth. If your net simply won't allow for things, like inferences to design for example, then your inquiry is no more likely to discover truth than the poor ichthyologist who was convinced that no sea creatures are less than two inches long.